release: 0.0.1

.gitignore

@@ -0,0 +1,3 @@
+/target
+.claude/
+.opencode/

Cargo.toml

@@ -0,0 +1,6 @@
+[workspace]
+members = ["lexer", "parser", "cli", "eval"]
+resolver = "3"
+
+[patch."ssh://git@git.rvba.fr:229/rvba/bimr-kernel.git"]
+bimr-kernel = { path = "../bimr-kernel" }

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 Milovann Yanatchkov
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

Makefile

@@ -0,0 +1,41 @@
+# bimr-engine — test targets.
+#
+# The fork-A eval is the experiment; the copied core (lexer, grammar,
+# parser) is the frozen harness. `make test` runs everything.
+
+.PHONY: test test-eval test-cli test-core clippy fmt check build run-sample
+
+test: test-core test-eval test-cli
+
+## Core — the copied harness, byte-identical to master
+test-core:
+	cargo test -p lexer -p parser
+
+## The experiment — eval unit tests
+test-eval:
+	cargo test -p eval
+
+## End-to-end — the cli gates on the wall corpus
+test-cli:
+	cargo test -p cli
+
+clippy:
+	cargo clippy --all-targets
+
+fmt:
+	cargo fmt
+
+fmt-check:
+	cargo fmt --check
+
+check:
+	cargo fmt --check && cargo clippy --all-targets && cargo test
+
+build:
+	cargo build
+
+## Replay the reference sample through the cli (output to /tmp — never
+## write back into the copied corpus)
+run-sample:
+	cargo run --quiet --bin bimr-cli -- build samples/bimr/wall.bimr --output /tmp/opencode/wall.ifcx
+	@cat /tmp/opencode/wall.ifcx

README.md

@@ -0,0 +1,3 @@
+# bimr-engine
+
+Parse and eval a ``.bimr`` file to generate a BIM model.

cli/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "cli"
+version = "0.0.1"
+edition = "2024"
+
+[[bin]]
+name = "bimr-cli"
+path = "src/main.rs"
+
+[dependencies]
+parser = { path = "../parser" }
+eval   = { path = "../eval" }
+clap   = { version = "4", features = ["derive"] }

cli/src/main.rs

@@ -0,0 +1,70 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+use clap::{Parser, Subcommand};
+use std::fs;
+use std::path::PathBuf;
+use std::process;
+
+#[derive(Parser)]
+#[clap(name = "bimr", version, about = "BIMR build tool")]
+struct Cli {
+    #[clap(subcommand)]
+    command: Command,
+}
+
+#[derive(Subcommand)]
+enum Command {
+    /// Compile a .bimr file to IFCX
+    Build {
+        /// Input .bimr source file
+        input: PathBuf,
+
+        /// Output path (default: <input>.ifcx)
+        #[clap(short, long)]
+        output: Option<PathBuf>,
+    },
+}
+
+/// Read a file to string.
+fn read_file(path: &PathBuf) -> Result<String, String> {
+    fs::read_to_string(path).map_err(|e| format!("Error reading {:?}: {e}", path))
+}
+
+/// Parse and evaluate a `.bimr` file, returning the entity store.
+pub fn compile(input: &PathBuf) -> Result<eval::Store, String> {
+    let src = read_file(input)?;
+    let program = parser::parse(&src).map_err(|errors| {
+        let msgs: Vec<String> = errors.iter().map(|e| format!("{e:?}")).collect();
+        format!("Parse errors:\n{}", msgs.join("\n"))
+    })?;
+    let file = input
+        .file_name()
+        .map(|n| n.to_string_lossy().to_string())
+        .unwrap_or_else(|| "model.bimr".to_string());
+    let store = eval::eval_program(&program, &file).map_err(|e| format!("Eval error: {e}"))?;
+    Ok(store)
+}
+
+fn main() {
+    let cli = Cli::parse();
+
+    if let Err(e) = run(cli.command) {
+        eprintln!("{e}");
+        process::exit(1);
+    }
+}
+
+fn run(command: Command) -> Result<(), String> {
+    match command {
+        Command::Build { input, output } => {
+            let store = compile(&input)?;
+            let (content, ext) = eval::to_output(&store);
+            let output_path = output.unwrap_or_else(|| input.with_extension(ext));
+            fs::write(&output_path, &content)
+                .map_err(|e| format!("Error writing {:?}: {e}", output_path))?;
+            eprintln!("→ {:?}", output_path);
+        }
+    }
+    Ok(())
+}

cli/tests/build.rs

@@ -0,0 +1,81 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! cli end-to-end (plan 3, S5): `bimr-cli build` on the wall corpus
+//! produces the compact BIMR source — master's format, with the
+//! documented self-reference fix (`Wall(l1, …)` not `Wall(w1, …)`).
+
+use std::fs;
+use std::path::PathBuf;
+use std::process::Command;
+
+/// Master's checked-in ifcx artifact for the corpus — the byte-parity target.
+const EXPECTED_IFCX: &str = include_str!("../../samples/bimr/wall.ifcx");
+
+/// Per-user, cargo-managed temp dir — never the shared /tmp (sticky-bit
+/// collisions across users, see the PermissionDenied incident).
+fn tmp(name: &str) -> PathBuf {
+    PathBuf::from(env!("CARGO_TARGET_TMPDIR")).join(name)
+}
+
+fn run_build(sample: &str, output: &PathBuf) -> Result<String, String> {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let input = PathBuf::from(root).join("../samples/bimr").join(sample);
+    let out = Command::new(env!("CARGO_BIN_EXE_bimr-cli"))
+        .args([
+            "build",
+            input.to_str().expect("utf8 path"),
+            "--output",
+            output.to_str().expect("utf8 path"),
+        ])
+        .output()
+        .map_err(|e| format!("spawn: {e}"))?;
+    if !out.status.success() {
+        return Err(format!(
+            "bimr-cli failed: {}",
+            String::from_utf8_lossy(&out.stderr)
+        ));
+    }
+    fs::read_to_string(output).map_err(|e| format!("read output: {e}"))
+}
+
+#[test]
+fn build_wall_bimr_emits_master_ifcx() {
+    let content = run_build("wall.bimr", &tmp("wall_out.ifcx")).expect("build ok");
+    assert_eq!(content, EXPECTED_IFCX);
+}
+
+#[test]
+fn build_rejects_unknown_constructors_cleanly() {
+    let sample = tmp("reject.bimr");
+    fs::write(&sample, "x = Frob(p1)\n").expect("write sample");
+    let out = Command::new(env!("CARGO_BIN_EXE_bimr-cli"))
+        .args(["build", sample.to_str().expect("utf8")])
+        .output()
+        .expect("spawn");
+    assert!(!out.status.success(), "List must be rejected");
+    let stderr = String::from_utf8_lossy(&out.stderr);
+    assert!(
+        stderr.contains("not supported"),
+        "rejection must name the failure: {stderr}"
+    );
+}
+
+#[test]
+fn build_output_defaults_to_ifcx_extension() {
+    // The cli default is <input>.ifcx (master parity) — run on a copy in the
+    // target tmpdir so the copied corpus is never rewritten.
+    let input = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../samples/bimr/wall.bimr");
+    let copy = tmp("wall_copy.bimr");
+    fs::copy(&input, &copy).expect("copy");
+    let out = Command::new(env!("CARGO_BIN_EXE_bimr-cli"))
+        .args(["build", copy.to_str().expect("utf8")])
+        .output()
+        .expect("spawn");
+    assert!(out.status.success());
+    let default_out = copy.with_extension("ifcx");
+    assert_eq!(
+        fs::read_to_string(&default_out).expect("read"),
+        EXPECTED_IFCX
+    );
+}

eval/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "eval"
+version = "0.0.1"
+edition = "2024"
+
+[dependencies]
+bimr = { package = "bimr-kernel", git = "ssh://git@git.rvba.fr:229/rvba/bimr-kernel.git" }
+parser = { path = "../parser" }
+serde_json = "1"

eval/src/error.rs

@@ -0,0 +1,53 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! One error type for the whole eval. Variants grow with the supported
+//! subset — never with machinery.
+
+use std::fmt;
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum Error {
+    /// A construct outside the supported subset — an unknown constructor.
+    Unsupported(&'static str),
+    /// A named reference that does not resolve to a stored node.
+    UnknownName(String),
+    /// An argument resolved to the wrong entity nature.
+    WrongNature {
+        name: String,
+        expected: &'static str,
+        got: &'static str,
+    },
+    /// A List argument carries the wrong element kind.
+    ListKind {
+        name: String,
+        expected: &'static str,
+        got: &'static str,
+    },
+    /// A name the engine needs to create is already taken.
+    NameCollision(String),
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Error::Unsupported(what) => write!(f, "not supported: {what}"),
+            Error::UnknownName(name) => write!(f, "unknown name `{name}`"),
+            Error::WrongNature {
+                name,
+                expected,
+                got,
+            } => write!(f, "`{name}` is a {got}, expected a {expected}"),
+            Error::ListKind {
+                name,
+                expected,
+                got,
+            } => write!(f, "`{name}` holds {got}, expected a list of {expected}"),
+            Error::NameCollision(name) => {
+                write!(f, "`{name}` is already taken")
+            }
+        }
+    }
+}
+
+impl std::error::Error for Error {}

eval/src/guid.rs

@@ -0,0 +1,74 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Identity — the engine-side `Guid`: name-derived deterministic GUIDs.
+//! Graph identity lives here, in the engine; the kernel stays untouched.
+//!
+//! Settled scheme ([`engine_entity.md`](https://git.rvba.fr/rvba/bimr-factory)):
+//! every GUID derives from its DSL origin. The hash is FNV-1a 64 — simple,
+//! stable across runs and platforms (std's `DefaultHasher` is neither).
+
+use std::fmt;
+
+/// Entity identity — 64-bit, `Copy`, cheap to store on every entity struct.
+///
+/// `Guid::from_name(file, name)` — deterministic, stable across re-runs and
+/// edits; a rename is a new identity.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord)]
+pub struct Guid(u64);
+
+impl Guid {
+    /// Deterministic GUID from the DSL origin: `stable_hash(file, name)`.
+    pub fn from_name(file: &str, name: &str) -> Guid {
+        let mut h: u64 = 0xcbf2_9ce4_8422_2325; // FNV offset basis
+        for b in file
+            .bytes()
+            .chain(std::iter::once(0x1f))
+            .chain(name.bytes())
+        {
+            h ^= b as u64;
+            h = h.wrapping_mul(0x0000_0100_0000_01b3); // FNV prime
+        }
+        Guid(h)
+    }
+}
+
+impl fmt::Display for Guid {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:016x}", self.0)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn deterministic_and_stable() {
+        let a = Guid::from_name("wall.py", "p1");
+        let b = Guid::from_name("wall.py", "p1");
+        assert_eq!(a, b);
+    }
+
+    #[test]
+    fn different_file_same_name() {
+        assert_ne!(
+            Guid::from_name("floor_01.py", "p1"),
+            Guid::from_name("floor_02.py", "p1")
+        );
+    }
+
+    #[test]
+    fn different_name_same_file() {
+        assert_ne!(
+            Guid::from_name("wall.py", "p1"),
+            Guid::from_name("wall.py", "p2")
+        );
+    }
+
+    #[test]
+    fn display() {
+        let g = Guid::from_name("wall.py", "p1");
+        assert_eq!(g.to_string().len(), 16);
+    }
+}

eval/src/lib.rs

@@ -0,0 +1,24 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! The BIMR evaluation engine.
+//!
+//! Whole-source evaluation of a parsed `.bimr` program: one `Node` shape
+//! `{ guid, entity, refs }`, GUID identity, two passes (structure, then
+//! geometry), no operator machinery. Entities are kernel types built at a
+//! single source; meshes are an on-demand per-node view.
+
+mod error;
+mod eval;
+pub mod guid;
+mod nodes;
+mod serialize;
+mod store;
+mod value;
+
+pub use error::Error;
+pub use eval::eval_program;
+pub use guid::Guid;
+pub use serialize::{to_bimr, to_ifcx, to_output};
+pub use store::Store;
+pub use value::Node;

eval/src/nodes/element/architecture/building.rs

@@ -0,0 +1,91 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Building — the whole engine story of `Building`.
+//!
+//! Nature lives in the kernel (`bimr::element::architecture::Building`): a
+//! named gathering of Storey entities **by value** — a container, no mesh.
+//! The storeys come from a List; the edge back to it lives in `refs`.
+
+use bimr::Entity;
+use bimr::element::architecture::Building as KernelBuilding;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{lookup, name_of, ref_name, str_of};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `b = Building("b03", storeys)` — positional or keyword form.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (building_name, source) = building_args(args)?;
+    let source_node = lookup(store, &source)?;
+    let storeys: Vec<Entity> = match &source_node.entity {
+        Entity::List(list) => {
+            if list.kind() != "Storey" {
+                return Err(Error::ListKind {
+                    name: source,
+                    expected: "Storey",
+                    got: list.kind(),
+                });
+            }
+            list.items().to_vec()
+        }
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+    let building = KernelBuilding::new(building_name, storeys);
+    store.insert(
+        file,
+        name,
+        Entity::Building(building),
+        vec![source_node.guid],
+    );
+    Ok(())
+}
+
+/// The compact BIMR text: `bld1 = Building("b03", storeys)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, b: &KernelBuilding) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = Building(\"{}\", {source_var})", b.name())
+}
+
+/// Building's argument mix: `Building("b03", src)` or
+/// `Building(name="b03", storeys=src)`.
+fn building_args(args: &[Argument]) -> Result<(String, String), Error> {
+    let mut building_name = None;
+    let mut source = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) if key == "name" => {
+                building_name = Some(str_of(expr)?);
+            }
+            Argument::Keyword(key, expr) if key == "storeys" => {
+                source = Some(name_of(expr)?);
+            }
+            Argument::Keyword(..) => return Err(Error::Unsupported("keyword argument")),
+            Argument::Positional(expr) => match expr {
+                parser::ast::Expression::String(_) if building_name.is_none() => {
+                    building_name = Some(str_of(expr)?);
+                }
+                _ if source.is_none() => source = Some(name_of(expr)?),
+                _ => return Err(Error::Unsupported("arity")),
+            },
+        }
+    }
+    match (building_name, source) {
+        (Some(building_name), Some(source)) => Ok((building_name, source)),
+        _ => Err(Error::Unsupported("arity")),
+    }
+}

eval/src/nodes/element/architecture/column.rs

@@ -0,0 +1,159 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Column — the whole engine story of `Column`.
+//!
+//! Nature lives in the kernel (`bimr::element::architecture::Column`): the
+//! struct, the constructor, the mesh. The engine holds the column's base
+//! **by value**; the edge back to the point node lives in `refs`.
+//!
+//! Lifting: a base that resolves to a List of Points produces a List of
+//! Columns — one per point, the scalars broadcast
+//! ([list_lifting](https://git.rvba.fr/rvba/bimr-factory)).
+
+use bimr::Entity;
+use bimr::element::architecture::Column as KernelColumn;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// IFCX path prefix — the per-type counter lives with the emitter.
+pub(crate) const IFCX_PREFIX: &str = "column";
+
+/// `c = Column(p, height, width, depth)` — both positional and keyword
+/// forms. `p` may be a List of Points: the call lifts into a List of
+/// Columns, one per point, the scalars broadcast.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (base, height, width, depth) = column_args(args)?;
+    let base_node = lookup(store, &base)?;
+    let items: Vec<Entity> = match &base_node.entity {
+        Entity::Point(p) => {
+            let col = KernelColumn::new(*p, height, width, depth);
+            store.insert(file, name, Entity::Column(col), vec![base_node.guid]);
+            return Ok(());
+        }
+        Entity::List(list) => {
+            if list.kind() != "Point" {
+                return Err(Error::ListKind {
+                    name: base,
+                    expected: "Point",
+                    got: list.kind(),
+                });
+            }
+            list.items().to_vec()
+        }
+        Entity::Divide(_) => {
+            // The created items — the record's output collection.
+            store
+                .outputs_of(base_node.guid)
+                .iter()
+                .map(|&guid| {
+                    let node = store.resolve(guid).expect("indexed");
+                    match node.entity {
+                        Entity::Point(p) => Entity::Point(p),
+                        ref other => unreachable!("divide items are Points: {}", other.type_name()),
+                    }
+                })
+                .collect::<Vec<_>>()
+        }
+        other => {
+            return Err(Error::WrongNature {
+                name: base,
+                expected: "Point",
+                got: other.type_name(),
+            });
+        }
+    };
+    lift(
+        store,
+        file,
+        name,
+        &items,
+        (height, width, depth),
+        vec![base_node.guid],
+    )
+}
+
+/// Lift: one Column per point, the scalars broadcast — a List of Columns
+/// with kind `"Column"`, `refs` pointing at the lifted-over source.
+fn lift(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    items: &[Entity],
+    scalars: (f64, f64, f64),
+    refs: Vec<crate::guid::Guid>,
+) -> Result<(), Error> {
+    let (height, width, depth) = scalars;
+    let cols = items
+        .iter()
+        .map(|item| match item {
+            Entity::Point(p) => KernelColumn::new(*p, height, width, depth),
+            other => unreachable!("lifting resolves Points: {}", other.type_name()),
+        })
+        .collect::<Vec<_>>();
+    let lifted = bimr::set::List::try_new(cols.into_iter().map(Entity::Column).collect::<Vec<_>>())
+        .expect("one Column per item — homogeneous");
+    store.insert(file, name, Entity::List(lifted), refs);
+    Ok(())
+}
+
+/// The compact BIMR text (reference format):
+/// `c1 = Column(p1, height=300, section_width=30, section_height=30)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, c: &KernelColumn) -> String {
+    let name = ref_name(store, node.guid);
+    let base_var = ref_name(store, node.refs[0]);
+    format!(
+        "{name} = Column({base_var}, height={}, section_width={}, section_height={})",
+        fmt_num(c.height),
+        fmt_num(c.section_width),
+        fmt_num(c.section_height)
+    )
+}
+
+/// Column's argument mix: `Column(p, 300, 30, 30)` or `Column(p, height=300,
+/// section_width=30, section_height=30)`. Any other keyword is rejected, not
+/// ignored.
+fn column_args(args: &[Argument]) -> Result<(String, f64, f64, f64), Error> {
+    let mut base = None;
+    let mut height = None;
+    let mut width = None;
+    let mut depth = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) if key == "height" => {
+                height = Some(number(expr)?);
+            }
+            Argument::Keyword(key, expr) if key == "section_width" => {
+                width = Some(number(expr)?);
+            }
+            Argument::Keyword(key, expr) if key == "section_height" => {
+                depth = Some(number(expr)?);
+            }
+            Argument::Keyword(..) => return Err(Error::Unsupported("keyword argument")),
+            Argument::Positional(expr) => {
+                if base.is_none() {
+                    base = Some(name_of(expr)?);
+                } else if height.is_none() {
+                    height = Some(number(expr)?);
+                } else if width.is_none() {
+                    width = Some(number(expr)?);
+                } else if depth.is_none() {
+                    depth = Some(number(expr)?);
+                }
+            }
+        }
+    }
+    match (base, height, width, depth) {
+        (Some(base), Some(height), Some(width), Some(depth)) => Ok((base, height, width, depth)),
+        _ => Err(Error::Unsupported("arity")),
+    }
+}

eval/src/nodes/element/architecture/frame.rs

@@ -0,0 +1,200 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Frame — the whole engine story of `Frame`.
+//!
+//! Nature lives in the kernel (`bimr::element::architecture::Frame`): a
+//! hollow rectangular solid — origin and end held **by value**, four
+//! section scalars. The edges back to the point nodes live in `refs`.
+//!
+//! Lifting: a single name argument lifts over a List of **pairs** (each a
+//! List of two Points — the shape `Explode` produces) — one Frame per pair,
+//! origin = pair[0], end = pair[1].
+
+use bimr::Entity;
+use bimr::element::architecture::Frame as KernelFrame;
+use bimr::geometry::Point;
+use parser::ast::{Argument, Expression};
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, ref_name, resolve};
+use crate::store::Store;
+use crate::value::Node;
+
+/// IFCX path prefix — the per-type counter lives with the emitter.
+pub(crate) const IFCX_PREFIX: &str = "frame";
+
+/// `f = Frame(origin, end, width, height, depth, thickness)` — both
+/// positional and keyword forms — or `frs = Frame(pairs, w, h, d, tk)`,
+/// lifting one Frame per pair.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (names, (width, height, depth, thickness)) = frame_args(args)?;
+    match names.len() {
+        2 => {
+            let origin_node = resolve(store, &names[0], "Point")?;
+            let end_node = resolve(store, &names[1], "Point")?;
+            let (o, e) = match (&origin_node.entity, &end_node.entity) {
+                (Entity::Point(o), Entity::Point(e)) => (*o, *e),
+                _ => unreachable!("resolve checked the nature"),
+            };
+            store.insert(
+                file,
+                name,
+                Entity::Frame(KernelFrame::new(o, e, width, height, depth, thickness)),
+                vec![origin_node.guid, end_node.guid],
+            );
+            Ok(())
+        }
+        1 => {
+            let source_node = lookup(store, &names[0])?;
+            let pairs = pairs_of(store, &names[0], source_node)?;
+            let frames = pairs
+                .into_iter()
+                .map(|(o, e)| {
+                    Entity::Frame(KernelFrame::new(o, e, width, height, depth, thickness))
+                })
+                .collect::<Vec<_>>();
+            let lifted =
+                bimr::set::List::try_new(frames).expect("one Frame per pair — homogeneous");
+            store.insert(file, name, Entity::List(lifted), vec![source_node.guid]);
+            Ok(())
+        }
+        _ => Err(Error::Unsupported("arity")),
+    }
+}
+
+/// The pairs a Frame lifts over: a List of Lists (each a pair of two
+/// Points) or an `Explode` record (its created parts are the pairs).
+fn pairs_of(store: &Store, name: &str, source: &Node) -> Result<Vec<(Point, Point)>, Error> {
+    let pair_lists: Vec<Entity> = match &source.entity {
+        Entity::Explode(_) => store
+            .outputs_of(source.guid)
+            .iter()
+            .map(|&guid| store.resolve(guid).expect("indexed").entity.clone())
+            .collect(),
+        Entity::List(list) => {
+            if list.kind() != "List" {
+                return Err(Error::ListKind {
+                    name: name.to_string(),
+                    expected: "List",
+                    got: list.kind(),
+                });
+            }
+            list.items().to_vec()
+        }
+        other => {
+            return Err(Error::WrongNature {
+                name: name.to_string(),
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+    pair_lists
+        .iter()
+        .map(|pair| match pair {
+            Entity::List(pair) => {
+                if pair.kind() != "Point" || pair.length() != 2 {
+                    return Err(Error::ListKind {
+                        name: name.to_string(),
+                        expected: "Point",
+                        got: pair.kind(),
+                    });
+                }
+                let (o, e) = match (pair.get(0), pair.get(1)) {
+                    (Some(Entity::Point(o)), Some(Entity::Point(e))) => (*o, *e),
+                    _ => unreachable!("kind `Point` checked"),
+                };
+                Ok((o, e))
+            }
+            other => Err(Error::WrongNature {
+                name: name.to_string(),
+                expected: "List",
+                got: other.type_name(),
+            }),
+        })
+        .collect()
+}
+
+/// The compact BIMR text (reference format):
+/// `fr1 = Frame(p1, p2, width=100, height=150, depth=12, thickness=5)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, f: &KernelFrame) -> String {
+    let name = ref_name(store, node.guid);
+    let origin_var = ref_name(store, node.refs[0]);
+    let end_var = ref_name(store, node.refs[1]);
+    let args = format!("{origin_var}, {end_var}");
+    format!("{name} = {}", scalars_suffix(&args, f))
+}
+
+/// The lifted compact form: `frs = Frame(ex1, width=…, …)` — the pair
+/// source is `refs[0]`; the scalars come from the first Frame (they are
+/// broadcast).
+pub(crate) fn to_bimr_lifted(store: &Store, node: &Node, f: &KernelFrame) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = {}", scalars_suffix(&source_var, f))
+}
+
+fn scalars_suffix(args: &str, f: &KernelFrame) -> String {
+    format!(
+        "Frame({args}, width={}, height={}, depth={}, thickness={})",
+        fmt_num(f.width),
+        fmt_num(f.height),
+        fmt_num(f.depth),
+        fmt_num(f.thickness)
+    )
+}
+
+/// Frame's scalars — width, height, depth, thickness.
+pub(crate) type Scalars = (f64, f64, f64, f64);
+
+/// Frame's argument mix. Identifiers become the point (or source) names,
+/// numbers fill width, height, depth, thickness in order; keywords name
+/// their scalar. Two names — the single form; one name — the lift.
+fn frame_args(args: &[Argument]) -> Result<(Vec<String>, Scalars), Error> {
+    let mut names: Vec<String> = Vec::new();
+    let mut numbers: Vec<f64> = Vec::new();
+    let mut width = None;
+    let mut height = None;
+    let mut depth = None;
+    let mut thickness = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) => match key.as_str() {
+                "width" => width = Some(number(expr)?),
+                "height" => height = Some(number(expr)?),
+                "depth" => depth = Some(number(expr)?),
+                "thickness" => thickness = Some(number(expr)?),
+                _ => return Err(Error::Unsupported("keyword argument")),
+            },
+            Argument::Positional(expr) => match expr {
+                Expression::Identifier(_) => names.push(name_of(expr)?),
+                _ => numbers.push(number(expr)?),
+            },
+        }
+    }
+    if names.is_empty() || names.len() > 2 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let numbers_len = numbers.len()
+        + width.is_some() as usize
+        + height.is_some() as usize
+        + depth.is_some() as usize
+        + thickness.is_some() as usize;
+    if numbers_len != 4 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let mut it = numbers.into_iter();
+    let scalars = (
+        width.unwrap_or_else(|| it.next().unwrap()),
+        height.unwrap_or_else(|| it.next().unwrap()),
+        depth.unwrap_or_else(|| it.next().unwrap()),
+        thickness.unwrap_or_else(|| it.next().unwrap()),
+    );
+    Ok((names, scalars))
+}

eval/src/nodes/element/architecture/mod.rs

@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Architecture element nodes — mirroring `bimr-kernel/src/element/architecture/`.
+
+pub(crate) mod building;
+pub(crate) mod column;
+pub(crate) mod frame;
+pub(crate) mod storey;
+pub(crate) mod slab;
+pub(crate) mod wall;

eval/src/nodes/element/architecture/slab.rs

@@ -0,0 +1,128 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Slab — the whole engine story of `Slab`.
+//!
+//! Nature lives in the kernel (`bimr::element::architecture::Slab`): a
+//! floor/ceiling plate — a polyline profile by value, thickness, elevation.
+//! The profile comes from a Curve (sampled at eight points per span), a
+//! List of Points, or a `Divide` record.
+
+use bimr::Entity;
+use bimr::element::architecture::Slab as KernelSlab;
+use bimr::geometry::Polyline;
+use bimr::math::Vec3;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// IFCX path prefix — the per-type counter lives with the emitter.
+pub(crate) const IFCX_PREFIX: &str = "slab";
+
+const SEGS_PER_SPAN: usize = 8;
+
+/// `s = Slab(source, thickness, elevation)` — positional or keyword form.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (source, thickness, elevation) = slab_args(args)?;
+    let source_node = lookup(store, &source)?;
+
+    let ring: Vec<Vec3> = match &source_node.entity {
+        Entity::List(list) => {
+            if list.kind() != "Point" {
+                return Err(Error::ListKind {
+                    name: source,
+                    expected: "Point",
+                    got: list.kind(),
+                });
+            }
+            points_of(list.items())?
+        }
+        Entity::Divide(_) => points_of(
+            &store
+                .outputs_of(source_node.guid)
+                .iter()
+                .map(|&guid| store.resolve(guid).expect("indexed").entity.clone())
+                .collect::<Vec<_>>(),
+        )?,
+        Entity::Curve(curve) => {
+            let n = curve.spline().control_points().len() * SEGS_PER_SPAN;
+            curve.points(n).iter().map(|p| p.to_vec3()).collect()
+        }
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+
+    let slab = KernelSlab::new(Polyline::new(ring), thickness, elevation);
+    store.insert(file, name, Entity::Slab(slab), vec![source_node.guid]);
+    Ok(())
+}
+
+fn points_of(items: &[Entity]) -> Result<Vec<Vec3>, Error> {
+    items
+        .iter()
+        .map(|item| match item {
+            Entity::Point(p) => Ok(p.to_vec3()),
+            other => Err(Error::ListKind {
+                name: String::new(),
+                expected: "Point",
+                got: other.type_name(),
+            }),
+        })
+        .collect()
+}
+
+/// The compact BIMR text: `s1 = Slab(crv, 150, 0)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, s: &KernelSlab) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!(
+        "{name} = Slab({source_var}, {}, {})",
+        fmt_num(s.thickness),
+        fmt_num(s.elevation)
+    )
+}
+
+/// Slab's argument mix: `Slab(src, t, e)` or
+/// `Slab(src, thickness=t, elevation=e)`. Any other keyword is rejected.
+fn slab_args(args: &[Argument]) -> Result<(String, f64, f64), Error> {
+    let mut source = None;
+    let mut thickness = None;
+    let mut elevation = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) if key == "thickness" => {
+                thickness = Some(number(expr)?);
+            }
+            Argument::Keyword(key, expr) if key == "elevation" => {
+                elevation = Some(number(expr)?);
+            }
+            Argument::Keyword(..) => return Err(Error::Unsupported("keyword argument")),
+            Argument::Positional(expr) => {
+                if source.is_none() {
+                    source = Some(name_of(expr)?);
+                } else if thickness.is_none() {
+                    thickness = Some(number(expr)?);
+                } else if elevation.is_none() {
+                    elevation = Some(number(expr)?);
+                }
+            }
+        }
+    }
+    match (source, thickness, elevation) {
+        (Some(source), Some(thickness), Some(elevation)) => Ok((source, thickness, elevation)),
+        _ => Err(Error::Unsupported("arity")),
+    }
+}

eval/src/nodes/element/architecture/storey.rs

@@ -0,0 +1,78 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Storey — the whole engine story of `Storey`.
+//!
+//! Nature lives in the kernel (`bimr::element::architecture::Storey`): a
+//! datum elevation gathering entities **by value** — a container, no mesh.
+//! The members come from a List (typically a lifted result); the edge back
+//! to it lives in `refs`.
+
+use bimr::Entity;
+use bimr::element::architecture::Storey as KernelStorey;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `l = Storey(elevation, source)` — positional or keyword form.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (elevation, source) = storey_args(args)?;
+    let source_node = lookup(store, &source)?;
+    let members: Vec<Entity> = match &source_node.entity {
+        Entity::List(list) => list.items().to_vec(),
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+    let storey = KernelStorey::new(elevation, members);
+    store.insert(file, name, Entity::Storey(storey), vec![source_node.guid]);
+    Ok(())
+}
+
+/// The compact BIMR text: `st1 = Storey(0, frames)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, l: &KernelStorey) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = Storey({}, {source_var})", fmt_num(l.elevation()))
+}
+
+/// Storey's argument mix: `Storey(z, src)` or `Storey(elevation=z, entities=src)`.
+fn storey_args(args: &[Argument]) -> Result<(f64, String), Error> {
+    let mut elevation = None;
+    let mut source = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) if key == "elevation" => {
+                elevation = Some(number(expr)?);
+            }
+            Argument::Keyword(key, expr) if key == "entities" => {
+                source = Some(name_of(expr)?);
+            }
+            Argument::Keyword(..) => return Err(Error::Unsupported("keyword argument")),
+            Argument::Positional(expr) => match expr {
+                parser::ast::Expression::Identifier(_) if source.is_none() => {
+                    source = Some(name_of(expr)?);
+                }
+                _ if elevation.is_none() => elevation = Some(number(expr)?),
+                _ if source.is_none() => source = Some(name_of(expr)?),
+                _ => return Err(Error::Unsupported("arity")),
+            },
+        }
+    }
+    match (elevation, source) {
+        (Some(elevation), Some(source)) => Ok((elevation, source)),
+        _ => Err(Error::Unsupported("arity")),
+    }
+}

eval/src/nodes/element/architecture/wall.rs

@@ -0,0 +1,85 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Wall — the whole engine story of `Wall`.
+//!
+//! Nature lives in the kernel (`bimr::element::architecture::Wall`): the
+//! struct, the constructor, the mesh. The engine holds the wall's line **by
+//! value**; the edge back to the line node lives in `refs`.
+
+use bimr::Entity;
+use bimr::element::architecture::Wall as KernelWall;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, name_of, number, ref_name, resolve};
+use crate::store::Store;
+use crate::value::Node;
+
+/// IFCX path prefix — the per-type counter lives with the emitter.
+pub(crate) const IFCX_PREFIX: &str = "wall";
+
+/// `w = Wall(l, width, height)` — both positional and keyword forms.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (line, width, height) = wall_args(args)?;
+    let line_node = resolve(store, &line, "Line")?;
+    let l = match &line_node.entity {
+        Entity::Line(l) => *l,
+        other => unreachable!("resolve checked the nature: {}", other.type_name()),
+    };
+    store.insert(
+        file,
+        name,
+        Entity::Wall(KernelWall::new(l, width, height)),
+        vec![line_node.guid],
+    );
+    Ok(())
+}
+
+/// The compact BIMR text: `w1 = Wall(l1, thickness=20, height=300)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, w: &KernelWall) -> String {
+    let name = ref_name(store, node.guid);
+    let line_var = ref_name(store, node.refs[0]);
+    format!(
+        "{name} = Wall({line_var}, thickness={}, height={})",
+        fmt_num(w.width),
+        fmt_num(w.height)
+    )
+}
+
+/// Wall's argument mix: `Wall(l1, 20, 300)` or `Wall(l1, thickness=20,
+/// height=300)`. Any other keyword is rejected, not ignored.
+fn wall_args(args: &[Argument]) -> Result<(String, f64, f64), Error> {
+    let mut line = None;
+    let mut width = None;
+    let mut height = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) if key == "thickness" => {
+                width = Some(number(expr)?);
+            }
+            Argument::Keyword(key, expr) if key == "height" => {
+                height = Some(number(expr)?);
+            }
+            Argument::Keyword(..) => return Err(Error::Unsupported("keyword argument")),
+            Argument::Positional(expr) => {
+                if line.is_none() {
+                    line = Some(name_of(expr)?);
+                } else if width.is_none() {
+                    width = Some(number(expr)?);
+                } else if height.is_none() {
+                    height = Some(number(expr)?);
+                }
+            }
+        }
+    }
+    match (line, width, height) {
+        (Some(line), Some(width), Some(height)) => Ok((line, width, height)),
+        _ => Err(Error::Unsupported("arity")),
+    }
+}

eval/src/nodes/element/mod.rs

@@ -0,0 +1,6 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Element nodes — mirroring `bimr-kernel/src/element/`.
+
+pub(crate) mod architecture;

eval/src/nodes/geometry/circle.rs

@@ -0,0 +1,57 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Circle — the whole engine story of `Circle`.
+//!
+//! Nature lives in the kernel (`bimr::geometry::Circle`): a curve primitive,
+//! center by value, radius; no mesh. The edge back to the center point node
+//! lives in `refs`.
+
+use bimr::Entity;
+use bimr::geometry::Circle as KernelCircle;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `c = Circle(p, radius)` — positional only.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = crate::nodes::positional_args(args)?;
+    if positional.len() != 2 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let center = name_of(positional[0])?;
+    let radius = number(positional[1])?;
+    let center_node = lookup(store, &center)?;
+    let p = match &center_node.entity {
+        Entity::Point(p) => *p,
+        other => {
+            return Err(Error::WrongNature {
+                name: center,
+                expected: "Point",
+                got: other.type_name(),
+            });
+        }
+    };
+    store.insert(
+        file,
+        name,
+        Entity::Circle(KernelCircle::new(p, radius)),
+        vec![center_node.guid],
+    );
+    Ok(())
+}
+
+/// The compact BIMR text: `c1 = Circle(p1, 200)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, c: &KernelCircle) -> String {
+    let name = ref_name(store, node.guid);
+    let center_var = ref_name(store, node.refs[0]);
+    format!("{name} = Circle({center_var}, {})", fmt_num(c.radius))
+}

eval/src/nodes/geometry/curve.rs

@@ -0,0 +1,102 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Curve — the whole engine story of `Curve`.
+//!
+//! Nature lives in the kernel (`bimr::geometry::Curve`): a closed
+//! Catmull-Rom spline through control points, sampled by `Divide`/`Cut`
+//! like the Circle. The engine holds the control points **by value** (via
+//! the kernel spline); the edge back to the source node lives in `refs`.
+//!
+//! The controls come from a List of Points or a `Divide` record.
+
+use bimr::Entity;
+use bimr::geometry::{Curve as KernelCurve, Spline};
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{lookup, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `c = Curve(ctrl)` — positional only. The source is a List of Points
+/// (at least three) or a `Divide` record (its created points).
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = crate::nodes::positional_args(args)?;
+    if positional.len() != 1 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let source = crate::nodes::name_of(positional[0])?;
+    let source_node = lookup(store, &source)?;
+
+    let points: Vec<bimr::geometry::Point> = match &source_node.entity {
+        Entity::List(list) => {
+            if list.kind() != "Point" {
+                return Err(Error::ListKind {
+                    name: source,
+                    expected: "Point",
+                    got: list.kind(),
+                });
+            }
+            let pts = list
+                .items()
+                .iter()
+                .map(|item| match item {
+                    Entity::Point(p) => *p,
+                    other => unreachable!("kind `{}` checked: {}", list.kind(), other.type_name()),
+                })
+                .collect::<Vec<_>>();
+            if pts.len() < 3 {
+                return Err(Error::Unsupported("arity"));
+            }
+            pts
+        }
+        Entity::Divide(_) | Entity::Random(_) => {
+            let pts = store
+                .outputs_of(source_node.guid)
+                .iter()
+                .map(|&guid| {
+                    let node = store.resolve(guid).expect("indexed");
+                    match node.entity {
+                        Entity::Point(p) => p,
+                        ref other => {
+                            unreachable!("operator items are Points: {}", other.type_name())
+                        }
+                    }
+                })
+                .collect::<Vec<_>>();
+            if pts.len() < 3 {
+                return Err(Error::Unsupported("arity"));
+            }
+            pts
+        }
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+
+    let ctrl = points
+        .into_iter()
+        .map(|p| bimr::math::Vec3::new(p.x, p.y, p.z))
+        .collect::<Vec<_>>();
+    let spline = Spline::new(ctrl).expect("at least three control points — gated");
+    let curve = KernelCurve::new(spline);
+    store.insert(file, name, Entity::Curve(curve), vec![source_node.guid]);
+    Ok(())
+}
+
+/// The compact BIMR text: `crv1 = Curve(ctrl)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, _c: &KernelCurve) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = Curve({source_var})")
+}

eval/src/nodes/geometry/extrusion.rs

@@ -0,0 +1,108 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Extrusion — the whole engine story of `Extrusion`.
+//!
+//! Nature lives in the kernel (`bimr::geometry::Extrusion`): the profile by
+//! value (E1 resolved — no handle), the sweep vector; `entity.mesh()` builds
+//! the side surface standalone. The engine keeps graph edges to the profile
+//! source and the vector in `refs`.
+//!
+//! The profile comes from a List of Lines or a `Cut` record (its created
+//! pieces); the sweep from a `Vector` node.
+
+use bimr::Entity;
+use bimr::geometry::Extrusion as KernelExtrusion;
+use bimr::geometry::Line;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{lookup, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// IFCX path prefix — the per-type counter lives with the emitter.
+pub(crate) const IFCX_PREFIX: &str = "extrusion";
+
+/// `e = Extrusion(profile, vec)` — positional only. The profile is a List of
+/// Lines (kind `"Line"`) or a `Cut` record; the sweep a `Vector`.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = crate::nodes::positional_args(args)?;
+    if positional.len() != 2 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let profile_name = crate::nodes::name_of(positional[0])?;
+    let vec_name = crate::nodes::name_of(positional[1])?;
+
+    let profile_node = lookup(store, &profile_name)?;
+    let profile: Vec<Line> = match &profile_node.entity {
+        Entity::List(list) => {
+            if list.kind() != "Line" {
+                return Err(Error::ListKind {
+                    name: profile_name,
+                    expected: "Line",
+                    got: list.kind(),
+                });
+            }
+            list.items()
+                .iter()
+                .map(|item| match item {
+                    Entity::Line(l) => *l,
+                    other => unreachable!("kind `{}` checked: {}", list.kind(), other.type_name()),
+                })
+                .collect()
+        }
+        Entity::Cut(_) => store
+            .outputs_of(profile_node.guid)
+            .iter()
+            .map(|&guid| {
+                let node = store.resolve(guid).expect("indexed");
+                match node.entity {
+                    Entity::Line(l) => l,
+                    ref other => unreachable!("cut pieces are Lines: {}", other.type_name()),
+                }
+            })
+            .collect(),
+        other => {
+            return Err(Error::WrongNature {
+                name: profile_name,
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+
+    let vec_node = lookup(store, &vec_name)?;
+    let vec = match &vec_node.entity {
+        Entity::Vector(v) => v.to_vec3(),
+        other => {
+            return Err(Error::WrongNature {
+                name: vec_name,
+                expected: "Vector",
+                got: other.type_name(),
+            });
+        }
+    };
+
+    let extrusion = KernelExtrusion::new(profile, vec);
+    store.insert(
+        file,
+        name,
+        Entity::Extrusion(extrusion),
+        vec![profile_node.guid, vec_node.guid],
+    );
+    Ok(())
+}
+
+/// The compact BIMR text: `e1 = Extrusion(ct1, v1)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, _e: &KernelExtrusion) -> String {
+    let name = ref_name(store, node.guid);
+    let profile_var = ref_name(store, node.refs[0]);
+    let vec_var = ref_name(store, node.refs[1]);
+    format!("{name} = Extrusion({profile_var}, {vec_var})")
+}

eval/src/nodes/geometry/line.rs

@@ -0,0 +1,62 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Line — the whole engine story of `Line`.
+//!
+//! Nature lives in the kernel (`bimr::geometry::Line`). The engine
+//! constructs it directly from the resolved point values; the graph edges
+//! are the two point GUIDs.
+
+use bimr::Entity;
+use bimr::geometry::Line as KernelLine;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{name_of, positional_args, ref_name, resolve};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `l = Line(p1, p2)` — both points resolved, both edges recorded.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.len() != 2 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let start_node = resolve(store, &name_of(positional[0])?, "Point")?;
+    let end_node = resolve(store, &name_of(positional[1])?, "Point")?;
+    let (start, end) = match (&start_node.entity, &end_node.entity) {
+        (Entity::Point(s), Entity::Point(e)) => (*s, *e),
+        _ => unreachable!("resolve checked the nature"),
+    };
+    store.insert(
+        file,
+        name,
+        Entity::Line(KernelLine::new(start, end)),
+        vec![start_node.guid, end_node.guid],
+    );
+    Ok(())
+}
+
+/// The compact BIMR text: `l1 = Line(p1, p2)`. Endpoints: the refs point at
+/// the point nodes — their DSL names are the emitted references.
+pub(crate) fn to_bimr(store: &Store, node: &Node, _l: &KernelLine) -> String {
+    let name = ref_name(store, node.guid);
+    format!(
+        "{name} = Line({}, {})",
+        endpoint_name(store, node, 0),
+        endpoint_name(store, node, 1)
+    )
+}
+
+fn endpoint_name(store: &Store, node: &Node, index: usize) -> String {
+    node.refs
+        .get(index)
+        .copied()
+        .map(|g| ref_name(store, g))
+        .unwrap_or_else(|| "?".to_string())
+}

eval/src/nodes/geometry/mod.rs

@@ -0,0 +1,11 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Geometry nodes — mirroring `bimr-kernel/src/geometry/`.
+
+pub(crate) mod circle;
+pub(crate) mod curve;
+pub(crate) mod extrusion;
+pub(crate) mod line;
+pub(crate) mod point;
+pub(crate) mod vector;

eval/src/nodes/geometry/point.rs

@@ -0,0 +1,48 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Point — the whole engine story of `Point`.
+//!
+//! Nature lives in the kernel (`bimr::geometry::Point`): the struct, the
+//! constructor, the payload. This file owns the engine faces: evaluation,
+//! construction, and the compact serialization text.
+
+use bimr::Entity;
+use bimr::geometry::Point as KernelPoint;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, number, positional_args, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `p = Point(x, y, z)` — a leaf, no refs.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.len() != 3 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let (x, y, z) = (
+        number(positional[0])?,
+        number(positional[1])?,
+        number(positional[2])?,
+    );
+    store.insert(file, name, Entity::Point(KernelPoint::new(x, y, z)), vec![]);
+    Ok(())
+}
+
+/// The compact BIMR text: `p1 = Point(0, 0, 0)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, p: &KernelPoint) -> String {
+    let name = ref_name(store, node.guid);
+    format!(
+        "{name} = Point({}, {}, {})",
+        fmt_num(p.x),
+        fmt_num(p.y),
+        fmt_num(p.z)
+    )
+}

eval/src/nodes/geometry/vector.rs

@@ -0,0 +1,52 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Vector — the whole engine story of `Vector`.
+//!
+//! Nature lives in the kernel (`bimr::geometry::Vector`): a 3D direction,
+//! a graph parameter like Grasshopper vectors. A leaf, no refs.
+
+use bimr::Entity;
+use bimr::geometry::Vector as KernelVector;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, number, positional_args, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `v = Vector(x, y, z)` — positional only.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.len() != 3 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let (x, y, z) = (
+        number(positional[0])?,
+        number(positional[1])?,
+        number(positional[2])?,
+    );
+    store.insert(
+        file,
+        name,
+        Entity::Vector(KernelVector::new(x, y, z)),
+        vec![],
+    );
+    Ok(())
+}
+
+/// The compact BIMR text: `v1 = Vector(0, 0, 300)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, v: &KernelVector) -> String {
+    let name = ref_name(store, node.guid);
+    format!(
+        "{name} = Vector({}, {}, {})",
+        fmt_num(v.x),
+        fmt_num(v.y),
+        fmt_num(v.z)
+    )
+}

eval/src/nodes/mod.rs

@@ -0,0 +1,194 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! The nodes — one file per entity, mirroring the kernel's taxonomy
+//! ([nodes layout](https://git.rvba.fr/rvba/bimr-factory/src/branch/main/task/refactor/2026-08-29/engine_nodes_layout.md)).
+//!
+//! Each node file owns the whole engine story of its entity: `eval`
+//! (argument extraction), `build`-style construction, the compact `to_bimr`
+//! text, and (for mesh-bearing entities) the IFCX path prefix. The dispatch
+//! is a plain match — no table, no `dyn`, no registry.
+
+pub(crate) mod element;
+pub(crate) mod geometry;
+pub(crate) mod operator;
+pub(crate) mod set;
+
+use bimr::Entity;
+use parser::ast::{Argument, Expression};
+
+use crate::error::Error;
+use crate::guid::Guid;
+use crate::store::Store;
+use crate::value::Node;
+
+/// Dispatch a DSL call to its node. Anything else is simply an unknown
+/// constructor — no blocklist, no categories.
+pub(crate) fn call(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    callee: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    match callee {
+        "Point" => geometry::point::eval(store, file, name, args),
+        "Line" => geometry::line::eval(store, file, name, args),
+        "Circle" => geometry::circle::eval(store, file, name, args),
+        "Curve" => geometry::curve::eval(store, file, name, args),
+        "Vector" => geometry::vector::eval(store, file, name, args),
+        "Extrusion" => geometry::extrusion::eval(store, file, name, args),
+        "Wall" => element::architecture::wall::eval(store, file, name, args),
+        "Column" => element::architecture::column::eval(store, file, name, args),
+        "Frame" => element::architecture::frame::eval(store, file, name, args),
+        "Slab" => element::architecture::slab::eval(store, file, name, args),
+        "Storey" => element::architecture::storey::eval(store, file, name, args),
+        "Building" => element::architecture::building::eval(store, file, name, args),
+        "Divide" => operator::divide::eval(store, file, name, args),
+        "Cut" => operator::cut::eval(store, file, name, args),
+        "Explode" => operator::explode::eval(store, file, name, args),
+        "Random" => operator::random::eval(store, file, name, args),
+        "List" => set::list::eval(store, file, name, args),
+        _ => Err(Error::Unsupported("call")),
+    }
+}
+
+/// The compact BIMR source line for one node — delegated to the node file.
+pub(crate) fn to_bimr(store: &Store, node: &Node) -> String {
+    match &node.entity {
+        Entity::Point(p) => geometry::point::to_bimr(store, node, p),
+        Entity::Line(l) => geometry::line::to_bimr(store, node, l),
+        Entity::Circle(c) => geometry::circle::to_bimr(store, node, c),
+        Entity::Curve(c) => geometry::curve::to_bimr(store, node, c),
+        Entity::Vector(v) => geometry::vector::to_bimr(store, node, v),
+        Entity::Extrusion(e) => geometry::extrusion::to_bimr(store, node, e),
+        Entity::Wall(w) => element::architecture::wall::to_bimr(store, node, w),
+        Entity::Column(c) => element::architecture::column::to_bimr(store, node, c),
+        Entity::Frame(f) => element::architecture::frame::to_bimr(store, node, f),
+        Entity::Slab(s) => element::architecture::slab::to_bimr(store, node, s),
+        Entity::Storey(l) => element::architecture::storey::to_bimr(store, node, l),
+        Entity::Building(b) => element::architecture::building::to_bimr(store, node, b),
+        Entity::List(l) => match l.kind() {
+            // A lifted list's compact form is the lifted statement itself —
+            // the constructor call over its source list (refs[0]). A plain
+            // binding can only reach these kinds by lifting, so the item
+            // kind alone selects the emitter.
+            "Column" => element::architecture::column::to_bimr(
+                store,
+                node,
+                match l.get(0) {
+                    Some(Entity::Column(c)) => c,
+                    _ => unreachable!("kind `Column` guarantees the payload"),
+                },
+            ),
+            "Frame" => element::architecture::frame::to_bimr_lifted(
+                store,
+                node,
+                match l.get(0) {
+                    Some(Entity::Frame(f)) => f,
+                    _ => unreachable!("kind `Frame` guarantees the payload"),
+                },
+            ),
+            _ => set::list::to_bimr(store, node, l),
+        },
+        Entity::Divide(d) => operator::divide::to_bimr(store, node, d),
+        Entity::Cut(c) => operator::cut::to_bimr(store, node, c),
+        Entity::Explode(e) => operator::explode::to_bimr(store, node, e),
+        Entity::Random(r) => operator::random::to_bimr(store, node, r),
+        other => panic!("to_bimr: unsupported entity {}", other.type_name()),
+    }
+}
+
+/// The IFCX path prefix of the node module owning this entity, if that
+/// module emits meshes.
+pub(crate) fn ifcx_prefix(entity: &Entity) -> Option<&'static str> {
+    match entity {
+        Entity::Wall(_) => Some(element::architecture::wall::IFCX_PREFIX),
+        Entity::Column(_) => Some(element::architecture::column::IFCX_PREFIX),
+        Entity::Frame(_) => Some(element::architecture::frame::IFCX_PREFIX),
+        Entity::Slab(_) => Some(element::architecture::slab::IFCX_PREFIX),
+        Entity::Extrusion(_) => Some(geometry::extrusion::IFCX_PREFIX),
+        _ => None,
+    }
+}
+
+// ── Shared plumbing ─────────────────────────────────────────────────────
+
+/// Resolve a DSL name to a stored node — any nature.
+pub(crate) fn lookup<'a>(store: &'a Store, name: &str) -> Result<&'a Node, Error> {
+    let guid = store
+        .named
+        .get(name)
+        .copied()
+        .ok_or_else(|| Error::UnknownName(name.to_string()))?;
+    Ok(store.resolve(guid).expect("indexed"))
+}
+
+/// Resolve a DSL name to a stored node of the expected nature.
+pub(crate) fn resolve<'a>(
+    store: &'a Store,
+    name: &str,
+    expected: &'static str,
+) -> Result<&'a Node, Error> {
+    let node = lookup(store, name)?;
+    let got = node.entity.type_name();
+    if got != expected {
+        return Err(Error::WrongNature {
+            name: name.to_string(),
+            expected,
+            got,
+        });
+    }
+    Ok(node)
+}
+
+/// Only positional arguments flow through here — `Wall` handles its own
+/// keyword mix (see `wall_args`). Keywords elsewhere are rejected, not
+/// silently ignored.
+pub(crate) fn positional_args(args: &[Argument]) -> Result<Vec<&Expression>, Error> {
+    args.iter()
+        .map(|arg| match arg {
+            Argument::Positional(expr) => Ok(expr),
+            Argument::Keyword(..) => Err(Error::Unsupported("keyword argument")),
+        })
+        .collect()
+}
+
+pub(crate) fn number(expr: &Expression) -> Result<f64, Error> {
+    match expr {
+        Expression::Integer(i) => Ok(*i as f64),
+        Expression::Float(f) => Ok(*f),
+        _ => Err(Error::Unsupported("numeric argument")),
+    }
+}
+
+pub(crate) fn name_of(expr: &Expression) -> Result<String, Error> {
+    match expr {
+        Expression::Identifier(name) => Ok(name.clone()),
+        _ => Err(Error::Unsupported("name argument")),
+    }
+}
+
+/// A string-literal argument — `Building("b03", …)`. The lexer keeps the
+/// surrounding quotes.
+pub(crate) fn str_of(expr: &Expression) -> Result<String, Error> {
+    match expr {
+        Expression::String(s) => Ok(s.trim_matches('"').to_string()),
+        _ => Err(Error::Unsupported("string argument")),
+    }
+}
+
+/// Format a float as a clean integer when it has no fractional part.
+pub(crate) fn fmt_num(x: f64) -> String {
+    if x.fract() == 0.0 && x.abs() < 1e15 {
+        format!("{}", x as i64)
+    } else {
+        format!("{x}")
+    }
+}
+
+/// The variable name a node is referenced by — its DSL name. Every node is
+/// named; there are no anonymous values.
+pub(crate) fn ref_name(store: &Store, guid: Guid) -> String {
+    store.name_of(guid).expect("named").to_string()
+}

eval/src/nodes/operator/cut.rs

@@ -0,0 +1,89 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Cut — the whole engine story of `Cut`.
+//!
+//! Nature lives in the kernel (`bimr::operator::Cut`): the source by value,
+//! the piece count, the cutting methods (circle first). Same record shape
+//! as `Divide`: the statement is a factory with a persistent root — the
+//! record stays (parametric), the pieces are created as named nodes edged
+//! to it, and resolving `d1` yields the created collection.
+
+use bimr::Entity;
+use bimr::operator::Cut as KernelCut;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, positional_args, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `ct = Cut(source, n)` — positional only. The source must be a Circle
+/// (the only cutting supported so far); `n` an integer ≥ 1.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.len() != 2 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let source = name_of(positional[0])?;
+    let n = count(positional[1])?;
+    let source_node = lookup(store, &source)?;
+    let source_entity = match &source_node.entity {
+        Entity::Circle(c) => Entity::Circle(*c),
+        Entity::Curve(c) => Entity::Curve(c.clone()),
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "Circle or Curve",
+                got: other.type_name(),
+            });
+        }
+    };
+
+    // The record first — items and consumers hang off it.
+    let cut = KernelCut::new(source_entity.clone(), n);
+    let record = store.insert(file, name, Entity::Cut(cut), vec![source_node.guid]);
+
+    // The created pieces: named `<binding>_<i>`, edges to the record. All
+    // names checked before any node is created.
+    let lines = KernelCut::new(source_entity, n)
+        .lines()
+        .map_err(|_| Error::Unsupported("cut"))?;
+    let mut names = Vec::with_capacity(n);
+    for i in 0..n {
+        let item_name = format!("{name}_{i}");
+        if store.named.contains_key(&item_name) {
+            return Err(Error::NameCollision(item_name));
+        }
+        names.push(item_name);
+    }
+    let mut items = Vec::with_capacity(n);
+    for (i, item_name) in names.iter().enumerate() {
+        let guid = store.insert(file, item_name, Entity::Line(lines[i]), vec![record]);
+        items.push(guid);
+    }
+    store.outputs.insert(record, items);
+    Ok(())
+}
+
+/// The piece count: an integral number ≥ 1.
+fn count(expr: &parser::ast::Expression) -> Result<usize, Error> {
+    let x = number(expr)?;
+    if x < 1.0 || x.fract() != 0.0 || x > usize::MAX as f64 {
+        return Err(Error::Unsupported("arity"));
+    }
+    Ok(x as usize)
+}
+
+/// The compact BIMR text: `ct1 = Cut(c1, 8)` — the record only; its created
+/// pieces are engine-owned and never reach the artifact.
+pub(crate) fn to_bimr(store: &Store, node: &Node, c: &KernelCut) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = Cut({source_var}, {})", fmt_num(c.n() as f64))
+}

eval/src/nodes/operator/divide.rs

@@ -0,0 +1,93 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Divide — the whole engine story of `Divide`.
+//!
+//! Nature lives in the kernel (`bimr::operator::Divide`): the source by
+//! value, the count, the division methods (circle division first). The
+//! engine holds the source **by value**; the edge back to the source node
+//! lives in `refs`.
+//!
+//! The statement is a factory with a persistent root: the Divide record
+//! stays (the parametric point a future engine regenerates from), and the
+//! divided entities are created as named nodes — `<binding>_<i>` — with
+//! edges back to the record. Resolving `d1` yields the created collection;
+//! `Column(d1, …)` lifts over it.
+
+use bimr::Entity;
+use bimr::operator::Divide as KernelDivide;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, positional_args, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `d = Divide(source, n)` — positional only. The source must be a Circle
+/// (the only division supported so far); `n` an integer ≥ 1.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.len() != 2 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let source = name_of(positional[0])?;
+    let n = count(positional[1])?;
+    let source_node = lookup(store, &source)?;
+    let source_entity = match &source_node.entity {
+        Entity::Circle(c) => Entity::Circle(*c),
+        Entity::Curve(c) => Entity::Curve(c.clone()),
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "Circle or Curve",
+                got: other.type_name(),
+            });
+        }
+    };
+    let divide = KernelDivide::new(source_entity.clone(), n);
+    let record = store.insert(file, name, Entity::Divide(divide), vec![source_node.guid]);
+
+    // The created entities: named `<binding>_<i>`, edges to the record. All
+    // names are checked before any node is created — a collision never
+    // leaves a partially built family.
+    let points = KernelDivide::new(source_entity, n)
+        .points()
+        .map_err(|_| Error::Unsupported("divide"))?;
+    let mut names = Vec::with_capacity(n);
+    for i in 0..n {
+        let item_name = format!("{name}_{i}");
+        if store.named.contains_key(&item_name) {
+            return Err(Error::NameCollision(item_name));
+        }
+        names.push(item_name);
+    }
+    let mut items = Vec::with_capacity(n);
+    for (i, item_name) in names.iter().enumerate() {
+        let guid = store.insert(file, item_name, Entity::Point(points[i]), vec![record]);
+        items.push(guid);
+    }
+    store.outputs.insert(record, items);
+    Ok(())
+}
+
+/// The division count: an integral number ≥ 1.
+fn count(expr: &parser::ast::Expression) -> Result<usize, Error> {
+    let x = number(expr)?;
+    if x < 1.0 || x.fract() != 0.0 || x > usize::MAX as f64 {
+        return Err(Error::Unsupported("arity"));
+    }
+    Ok(x as usize)
+}
+
+/// The compact BIMR text: `d1 = Divide(c1, 8)` — the record only; its
+/// created items are engine-owned and never reach the artifact.
+pub(crate) fn to_bimr(store: &Store, node: &Node, d: &KernelDivide) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = Divide({source_var}, {})", fmt_num(d.n() as f64))
+}

eval/src/nodes/operator/explode.rs

@@ -0,0 +1,88 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Explode — the whole engine story of `Explode`.
+//!
+//! Nature lives in the kernel (`bimr::operator::Explode`): a Line into its
+//! two endpoints, a List of Lines into pairs (each pair a List of two
+//! Points). Same record shape as `Divide`/`Cut`: the statement is a factory
+//! with a persistent root — the record stays, the parts are created as
+//! named nodes edged to it, and resolving `ex1` yields the created
+//! collection. `Frame(ex1, …)` lifts one Frame per pair.
+
+use bimr::Entity;
+use bimr::operator::Explode as KernelExplode;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{lookup, name_of, positional_args, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `ex = Explode(source)` — positional only. The source is a Line (two
+/// endpoints) or a List of Lines / a `Cut` record (one pair per line).
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.len() != 1 {
+        return Err(Error::Unsupported("arity"));
+    }
+    let source = name_of(positional[0])?;
+    let source_node = lookup(store, &source)?;
+
+    // Normalize the source into a kernel Entity for the explosion.
+    let source_entity = match &source_node.entity {
+        Entity::Cut(_) => {
+            let lines: Vec<Entity> = store
+                .outputs_of(source_node.guid)
+                .iter()
+                .map(|&guid| {
+                    let node = store.resolve(guid).expect("indexed");
+                    match node.entity {
+                        Entity::Line(l) => Entity::Line(l),
+                        ref other => unreachable!("cut pieces are Lines: {}", other.type_name()),
+                    }
+                })
+                .collect();
+            Entity::List(bimr::set::List::try_new(lines).expect("cut pieces — all Lines"))
+        }
+        entity => entity.clone(),
+    };
+
+    // The record first — items and consumers hang off it.
+    let explode = KernelExplode::new(source_entity.clone());
+    let record = store.insert(file, name, Entity::Explode(explode), vec![source_node.guid]);
+
+    // The created parts: named `<binding>_<i>`, edges to the record. All
+    // names checked before any node is created.
+    let parts = KernelExplode::new(source_entity)
+        .parts()
+        .map_err(|_| Error::Unsupported("explode"))?;
+    let mut names = Vec::with_capacity(parts.len());
+    for i in 0..parts.len() {
+        let item_name = format!("{name}_{i}");
+        if store.named.contains_key(&item_name) {
+            return Err(Error::NameCollision(item_name));
+        }
+        names.push(item_name);
+    }
+    let mut items = Vec::with_capacity(parts.len());
+    for (i, item_name) in names.iter().enumerate() {
+        let guid = store.insert(file, item_name, parts[i].clone(), vec![record]);
+        items.push(guid);
+    }
+    store.outputs.insert(record, items);
+    Ok(())
+}
+
+/// The compact BIMR text: `ex1 = Explode(ct1)` — the record only; its
+/// created parts are engine-owned and never reach the artifact.
+pub(crate) fn to_bimr(store: &Store, node: &Node, _e: &KernelExplode) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!("{name} = Explode({source_var})")
+}

eval/src/nodes/operator/mod.rs

@@ -0,0 +1,9 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+// Operator nodes — mirroring the kernel's `operator` taxonomy.
+
+pub(crate) mod cut;
+pub(crate) mod divide;
+pub(crate) mod explode;
+pub(crate) mod random;

eval/src/nodes/operator/random.rs

@@ -0,0 +1,124 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Random — the whole engine story of `Random`.
+//!
+//! Nature lives in the kernel (`bimr::operator::Random`): a seeded
+//! displacement of a List of Points — dims=2 keeps the elevation. Same
+//! record shape as `Divide`/`Cut`/`Explode`: the statement is a factory
+//! with a persistent root; the displaced points are created as named nodes
+//! edged to it. `Curve(r1, …)` consumes them.
+
+use bimr::Entity;
+use bimr::operator::Random as KernelRandom;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{fmt_num, lookup, name_of, number, ref_name};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `r = Random(source, seed=…, min=…, max=…, dims=…)` — the source
+/// positional; dims defaults to 2.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let (source, seed, min, max, dims) = random_args(args)?;
+    let source_node = lookup(store, &source)?;
+    let source_entity = match &source_node.entity {
+        Entity::List(list) => {
+            if list.kind() != "Point" {
+                return Err(Error::ListKind {
+                    name: source,
+                    expected: "Point",
+                    got: list.kind(),
+                });
+            }
+            source_node.entity.clone()
+        }
+        other => {
+            return Err(Error::WrongNature {
+                name: source,
+                expected: "List",
+                got: other.type_name(),
+            });
+        }
+    };
+
+    // The record first — items and consumers hang off it.
+    let random = KernelRandom::new(source_entity.clone(), seed, min, max, dims);
+    let record = store.insert(file, name, Entity::Random(random), vec![source_node.guid]);
+
+    // The displaced points: named `<binding>_<i>`, edges to the record.
+    // All names checked before any node is created.
+    let points = KernelRandom::new(source_entity, seed, min, max, dims)
+        .displaced()
+        .map_err(|_| Error::Unsupported("random"))?;
+    let mut names = Vec::with_capacity(points.len());
+    for i in 0..points.len() {
+        let item_name = format!("{name}_{i}");
+        if store.named.contains_key(&item_name) {
+            return Err(Error::NameCollision(item_name));
+        }
+        names.push(item_name);
+    }
+    let mut items = Vec::with_capacity(points.len());
+    for (i, item_name) in names.iter().enumerate() {
+        let guid = store.insert(file, item_name, Entity::Point(points[i]), vec![record]);
+        items.push(guid);
+    }
+    store.outputs.insert(record, items);
+    Ok(())
+}
+
+/// Random's argument mix: the source positional, the scalars by keyword —
+/// `Random(base, seed=128, min=-150, max=150, dims=2)`. `dims` defaults
+/// to 2. Any other keyword is rejected.
+fn random_args(args: &[Argument]) -> Result<(String, u64, f64, f64, u8), Error> {
+    let mut source = None;
+    let mut seed = None;
+    let mut min = None;
+    let mut max = None;
+    let mut dims = None;
+    for arg in args {
+        match arg {
+            Argument::Keyword(key, expr) => match key.as_str() {
+                "seed" => seed = Some(number(expr)? as u64),
+                "min" => min = Some(number(expr)?),
+                "max" => max = Some(number(expr)?),
+                "dims" => dims = Some(number(expr)? as u8),
+                _ => return Err(Error::Unsupported("keyword argument")),
+            },
+            Argument::Positional(expr) => {
+                if source.is_none() {
+                    source = Some(name_of(expr)?);
+                } else {
+                    return Err(Error::Unsupported("arity"));
+                }
+            }
+        }
+    }
+    match (source, seed, min, max) {
+        (Some(source), Some(seed), Some(min), Some(max)) => {
+            Ok((source, seed, min, max, dims.unwrap_or(2)))
+        }
+        _ => Err(Error::Unsupported("arity")),
+    }
+}
+
+/// The compact BIMR text:
+/// `r1 = Random(base, seed=128, min=-150, max=150, dims=2)`.
+pub(crate) fn to_bimr(store: &Store, node: &Node, r: &KernelRandom) -> String {
+    let name = ref_name(store, node.guid);
+    let source_var = ref_name(store, node.refs[0]);
+    format!(
+        "{name} = Random({source_var}, seed={}, min={}, max={}, dims={})",
+        fmt_num(r.seed() as f64),
+        fmt_num(r.min()),
+        fmt_num(r.max()),
+        fmt_num(r.dims() as f64)
+    )
+}

eval/src/nodes/set/list.rs

@@ -0,0 +1,68 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! List — the whole engine story of `List`.
+//!
+//! Nature lives in the kernel (`bimr::set::List`): homogeneous by
+//! construction, the element kind taken from the first item. The engine
+//! resolves every item by name before calling the kernel constructor; the
+//! graph edges are the item GUIDs.
+
+use bimr::Entity;
+use bimr::set::List as KernelList;
+use parser::ast::Argument;
+
+use crate::error::Error;
+use crate::nodes::{lookup, name_of, positional_args, ref_name, resolve};
+use crate::store::Store;
+use crate::value::Node;
+
+/// `lst = List(p1, p2, …)` — identifier references only, at least one item.
+/// The first item may be of any nature — it sets the element kind; every
+/// later item must match it.
+pub(crate) fn eval(
+    store: &mut Store,
+    file: &str,
+    name: &str,
+    args: &[Argument],
+) -> Result<(), Error> {
+    let positional = positional_args(args)?;
+    if positional.is_empty() {
+        return Err(Error::Unsupported("arity"));
+    }
+    let names = positional
+        .iter()
+        .map(|e| name_of(e))
+        .collect::<Result<Vec<_>, _>>()?;
+
+    let mut kind: Option<&'static str> = None;
+    let mut refs = Vec::with_capacity(names.len());
+    let mut items = Vec::with_capacity(names.len());
+    for n in &names {
+        let node = match kind {
+            None => lookup(store, n)?,
+            Some(k) => resolve(store, n, k)?,
+        };
+        refs.push(node.guid);
+        items.push(node.entity.clone());
+        kind = Some(node.entity.type_name());
+    }
+
+    let list = KernelList::try_new(items).expect("homogeneous by resolution");
+    store.insert(file, name, Entity::List(list), refs);
+    Ok(())
+}
+
+/// The compact BIMR text of a plain list: `lst1 = List(p1, p2)`.
+/// Lifted lists (item kind = a constructor nature) emit their lifted
+/// statement instead — the dispatch lives in [`crate::nodes::to_bimr`].
+pub(crate) fn to_bimr(store: &Store, node: &Node, _l: &KernelList) -> String {
+    let name = ref_name(store, node.guid);
+    let items = node
+        .refs
+        .iter()
+        .map(|g| ref_name(store, *g))
+        .collect::<Vec<_>>()
+        .join(", ");
+    format!("{name} = List({items})")
+}

eval/src/nodes/set/mod.rs

@@ -0,0 +1,6 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+// Set nodes — mirroring the kernel's `set` taxonomy.
+
+pub(crate) mod list;

eval/src/serialize.rs

@@ -0,0 +1,179 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Serialization — compact BIMR source that reconstructs the model.
+//!
+//! Format rules: `fmt_num`, `"{}, {}, {}"` points, keyword-form Wall. The
+//! compact form references entities by their DSL names (`w1 = Wall(l1, …)`)
+//! so the emitted source reconstructs the model — that is the whole point.
+//!
+//! Geometry is an on-demand per-node view: emitters call `entity.mesh()`
+//! directly and skip non-mesh-bearing entities. No cache, no side-table —
+//! no geometric detail lives outside the kernel. A memoized view arrives
+//! only when relations demand it.
+
+use serde_json::json;
+
+use crate::nodes;
+use crate::store::Store;
+
+/// Emit BIMR DSL source that reconstructs the model held in `store`.
+///
+/// The walk is the **statements log**, not the arena: a `Divide`'s created
+/// items are engine-owned nodes (they never reach the artifact — the compact
+/// `Divide` form regenerates them on eval). Named statements emit in
+/// construction order; the per-entity text lives in the node modules.
+pub fn to_bimr(store: &Store) -> String {
+    store
+        .statements
+        .iter()
+        .map(|&guid| {
+            let node = store.resolve(guid).expect("indexed");
+            nodes::to_bimr(store, node)
+        })
+        .collect::<Vec<_>>()
+        .join("\n")
+}
+
+/// Output content + file extension for the cli `build` command.
+///
+/// The IFCX document is the build artifact. The compact BIMR source (above)
+/// is the round-trip artifact, covered by tests.
+pub fn to_output(store: &Store) -> (String, &'static str) {
+    (to_ifcx(store), "ifcx")
+}
+
+/// Emit an IFCX document compatible with the buildingSMART IFC5 viewer.
+///
+/// Same shape as the reference IFCX format: one data entry per
+/// mesh-bearing entity, `wall-001`-style paths in construction order.
+/// Validated byte-for-byte against the checked-in `samples/bimr/wall.ifcx`.
+pub fn to_ifcx(store: &Store) -> String {
+    let mut data: Vec<serde_json::Value> = Vec::new();
+    // One counter per node-module prefix (`wall-001`, later `column-001`).
+    let mut counters: std::collections::HashMap<&'static str, usize> = Default::default();
+    for node in &store.arena {
+        // A lifted List is not mesh-bearing itself; its items are. One entry
+        // per item, counters keyed by the item kind (`column-001` …).
+        let items: &[bimr::Entity] = match &node.entity {
+            bimr::Entity::List(list) => list.items(),
+            _ => std::slice::from_ref(&node.entity),
+        };
+        for item in items {
+            let Some(mesh) = item.mesh() else {
+                continue;
+            };
+            let prefix =
+                nodes::ifcx_prefix(item).expect("a mesh-bearing entity always has a node module");
+            let n = counters.entry(prefix).or_insert(0);
+            *n += 1;
+            data.push(json!({
+                "path": format!("{prefix}-{:03}", n),
+                "attributes": {
+                    "usd::usdgeom::mesh": {
+                        "points": mesh.points,
+                        "faceVertexIndices": mesh.indices,
+                    }
+                }
+            }));
+        }
+    }
+    let doc = json!({
+        "header": {
+            "ifcxVersion": "ifcx_alpha",
+            "dataVersion": "1.0.0"
+        },
+        "imports": [
+            { "uri": "https://ifcx.dev/@openusd.org/usd@v1.ifcx" }
+        ],
+        "schemas": {},
+        "data": data
+    });
+    serde_json::to_string_pretty(&doc).unwrap()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::eval::eval_program;
+    use parser::ast::Program;
+    use serde_json::Value as JsonValue;
+
+    const WALL: &str = concat!(
+        "p1 = Point(0,0,0)\n",
+        "p2 = Point(500,0,0)\n",
+        "l1 = Line(p1,p2)\n",
+        "w1 = Wall(l1,20,300)\n",
+    );
+
+    /// The reference compact form for the same corpus: the wall references
+    /// its line by name (`w1 = Wall(l1, …)`), so the emitted source
+    /// reconstructs the model.
+    const WALL_COMPACT: &str = concat!(
+        "p1 = Point(0, 0, 0)\n",
+        "p2 = Point(500, 0, 0)\n",
+        "l1 = Line(p1, p2)\n",
+        "w1 = Wall(l1, thickness=20, height=300)",
+    );
+
+    /// The checked-in ifcx artifact for the corpus — the byte-parity
+    /// target.
+    const WALL_IFCX: &str = include_str!("../../samples/bimr/wall.ifcx");
+
+    fn wall_store() -> Store {
+        let program: Program = parser::parse(WALL).expect("parse ok");
+        eval_program(&program, "wall.bimr").expect("eval ok")
+    }
+
+    #[test]
+    fn compact_form_matches_reference_format() {
+        let store = wall_store();
+        assert_eq!(to_bimr(&store), WALL_COMPACT);
+    }
+
+    #[test]
+    fn ifcx_matches_reference_artifact() {
+        let store = wall_store();
+        assert_eq!(to_ifcx(&store), WALL_IFCX);
+    }
+
+    #[test]
+    fn ifcx_renders_one_mesh_entity() {
+        let store = wall_store();
+        let doc: JsonValue = serde_json::from_str(&to_ifcx(&store)).unwrap();
+        let data = doc["data"].as_array().unwrap();
+        assert_eq!(data.len(), 1);
+        assert_eq!(data[0]["path"], json!("wall-001"));
+        let mesh = &data[0]["attributes"]["usd::usdgeom::mesh"];
+        assert_eq!(mesh["points"].as_array().unwrap().len(), 24);
+        assert_eq!(mesh["faceVertexIndices"].as_array().unwrap().len(), 36);
+        assert_eq!(doc["header"]["ifcxVersion"], json!("ifcx_alpha"));
+    }
+
+    #[test]
+    fn round_trip_is_stable() {
+        // to_bimr → parse → eval → to_bimr must be a fixed point.
+        let store1 = wall_store();
+        let src2 = to_bimr(&store1);
+        let program2: Program = parser::parse(&src2).expect("round-trip parses");
+        let store2 = eval_program(&program2, "wall.bimr").expect("round-trip evals");
+        assert_eq!(to_bimr(&store2), src2);
+    }
+
+    #[test]
+    fn round_tripped_model_has_same_geometry() {
+        let store1 = wall_store();
+        let src2 = to_bimr(&store1);
+        let program2: Program = parser::parse(&src2).expect("round-trip parses");
+        let store2 = eval_program(&program2, "wall.bimr").expect("round-trip evals");
+        assert_eq!(to_ifcx(&store1), to_ifcx(&store2));
+    }
+
+    #[test]
+    fn floats_stay_floats() {
+        let src = "a = Point(0.5, 1.25, -2.0)\n";
+        let program: Program = parser::parse(src).expect("parse ok");
+        let store = eval_program(&program, "f.bimr").expect("eval ok");
+        assert_eq!(to_bimr(&store), "a = Point(0.5, 1.25, -2)");
+    }
+}

eval/src/store.rs

@@ -0,0 +1,130 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! The Store — ordered arena of nodes, indexed by GUID.
+//!
+//! Goal 3: the eval owns identity + graph edges + the ordered construction
+//! log — nothing else. Goal 2: every node is named; its GUID is
+//! `Guid::from_name(file, name)`.
+
+use std::collections::HashMap;
+
+use crate::guid::Guid;
+
+use crate::value::Node;
+
+#[derive(Debug, Default)]
+pub struct Store {
+    /// Insertion order — the construction log.
+    pub arena: Vec<Node>,
+    /// GUID → arena slot.
+    pub guid_index: HashMap<Guid, usize>,
+    /// The ordered GUID log — the construction order.
+    pub order: Vec<Guid>,
+    /// DSL name → GUID (the name IS the stable guid).
+    pub named: HashMap<String, Guid>,
+    /// Record → the nodes it created — the construction tree's edges.
+    /// A `Divide` maps to its divided items; regeneration (future) walks
+    /// these from the changed record down.
+    pub outputs: HashMap<Guid, Vec<Guid>>,
+    /// The binding GUID of each source statement, in order — the walk
+    /// `to_bimr` emits. Engine-created nodes (a Divide's items) are in the
+    /// arena but are not statements, so they never reach the artifact.
+    pub statements: Vec<Guid>,
+}
+
+impl Store {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Insert a node: attach identity as data, record the edge list, log the
+    /// GUID. Every node is named — the GUID is `Guid::from_name(file, name)`.
+    pub fn insert(
+        &mut self,
+        file: &str,
+        name: &str,
+        entity: bimr::Entity,
+        refs: Vec<Guid>,
+    ) -> Guid {
+        let guid = Guid::from_name(file, name);
+        self.named.insert(name.to_string(), guid);
+        let slot = self.arena.len();
+        self.arena.push(Node { guid, entity, refs });
+        self.guid_index.insert(guid, slot);
+        self.order.push(guid);
+        guid
+    }
+
+    /// Resolve a GUID to its node.
+    pub fn resolve(&self, guid: Guid) -> Option<&Node> {
+        self.guid_index.get(&guid).map(|&slot| &self.arena[slot])
+    }
+
+    /// The nodes a record created, in order.
+    pub fn outputs_of(&self, guid: Guid) -> &[Guid] {
+        self.outputs.get(&guid).map(Vec::as_slice).unwrap_or(&[])
+    }
+
+    /// Reverse lookup: the DSL name of a GUID, if it has one.
+    pub fn name_of(&self, guid: Guid) -> Option<&str> {
+        self.named
+            .iter()
+            .find(|entry| *entry.1 == guid)
+            .map(|(name, _)| name.as_str())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use bimr::geometry::Point;
+
+    #[test]
+    fn named_insert_assigns_stable_guid() {
+        let mut store = Store::new();
+        let g = store.insert(
+            "wall.bimr",
+            "p1",
+            bimr::Entity::Point(Point::new(0.0, 0.0, 0.0)),
+            vec![],
+        );
+        assert_eq!(g, Guid::from_name("wall.bimr", "p1"));
+        assert_eq!(store.named["p1"], g);
+        assert_eq!(store.resolve(g).unwrap().guid, g);
+    }
+
+    #[test]
+    fn arena_is_the_construction_log() {
+        let mut store = Store::new();
+        let g1 = store.insert(
+            "wall.bimr",
+            "p1",
+            bimr::Entity::Point(Point::new(0.0, 0.0, 0.0)),
+            vec![],
+        );
+        let g2 = store.insert(
+            "wall.bimr",
+            "p2",
+            bimr::Entity::Point(Point::new(500.0, 0.0, 0.0)),
+            vec![],
+        );
+        assert_eq!(store.order, vec![g1, g2]);
+        assert_eq!(
+            store.arena.iter().map(|n| n.guid).collect::<Vec<_>>(),
+            vec![g1, g2]
+        );
+    }
+
+    #[test]
+    fn name_of_reverse_lookup() {
+        let mut store = Store::new();
+        let g = store.insert(
+            "wall.bimr",
+            "p1",
+            bimr::Entity::Point(Point::new(0.0, 0.0, 0.0)),
+            vec![],
+        );
+        assert_eq!(store.name_of(g), Some("p1"));
+    }
+}

eval/src/value.rs

@@ -0,0 +1,21 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+//! Identity + graph edges + the entity, in one shape.
+//!
+//! Goal 1 (single-source): the engine stores the **kernel** entity directly —
+//! there is no mirror and this file declares no per-entity variant.
+//! Goal 2 (identity as data): every node carries its GUID; references are
+//! GUIDs.
+
+use crate::guid::Guid;
+use bimr::Entity;
+
+/// The one node shape of the engine.
+#[derive(Debug, Clone)]
+pub struct Node {
+    pub guid: Guid,
+    pub entity: Entity,
+    /// Graph edges — the entities this node was built from.
+    pub refs: Vec<Guid>,
+}

grammar/README.md

@@ -0,0 +1,21 @@
+# Grammar
+
+`bimr.bnf` is a human-readable reference describing the BIMR language grammar in BNF notation. It is not consumed by the build — it documents the rules that the lexer and parser implement in code.
+
+## How the pipeline works
+
+**Lexer** (`lexer/src/lexer.rs`) — powered by [`logos`](https://github.com/maciejhirsz/logos). The grammar is expressed directly as Rust attributes on the `Token` enum: regex patterns for identifiers, integers, and strings; literal patterns for punctuation (`=`, `,`, `(`, `)`). `logos` generates the tokeniser at compile time — no external grammar file is involved.
+
+**Parser** (`parser/src/parser.rs`) — powered by [`chumsky`](https://github.com/zesterer/chumsky). Consumes the token stream produced by the lexer and builds an AST. The grammar rules map directly to parser combinators:
+
+| BNF rule | Parser combinator |
+|---|---|
+| `program ::= statement*` | `statement().repeated().collect()` |
+| `statement ::= identifier = expression` | `identifier().then_ignore(just(Equal)).then(expression())` |
+| `expression ::= function_call \| identifier \| integer \| string` | `choice((function_call, base_expr()))` |
+| `function_call ::= identifier ( arguments )` | `identifier().then(...).delimited_by(LeftParen, RightParen)` |
+| `arguments ::= expression (, expression)*` | `base_expr().separated_by(just(Comma))` |
+
+## Summary
+
+`bimr.bnf` serves as a concise spec to understand the language at a glance. The source of truth is the Rust code in `lexer/` and `parser/`.

grammar/bimr.bnf

@@ -0,0 +1,5 @@
+program ::= statement*
+statement ::= identifier = expression
+expression ::= function_call | identifier | integer | string
+function_call ::= identifier ( arguments )
+arguments ::= expression ( , expression )* | 

lexer/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "lexer"
+version = "0.0.1"
+edition = "2024"
+
+[dependencies]
+logos = "0.15"
+clap = { version = "4.5", features = ["derive"] }
+
+[lib]
+name = "lexer"
+path = "src/lib.rs"

lexer/README.md

@@ -0,0 +1 @@
+# BIMR parser

lexer/src/lexer.rs

@@ -0,0 +1,191 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+use logos::{Lexer, Logos, Skip};
+use std::fmt;
+
+/// Tokens produced by the BIMR DSL lexer.
+///
+/// Whitespace (spaces, tabs, carriage returns) is silently skipped.
+/// Line comments (`#` up to the end of the line) are also skipped.
+/// Newlines are consumed by `newline_callback` to track line/column position
+/// for error reporting; they do not appear in the token stream.
+///
+/// Floats are stored as raw `u64` bit patterns because `f64` does not implement
+/// `Hash` or `Eq`. Reconstruct the value with `f64::from_bits(bits)`.
+#[derive(Logos, Debug, PartialEq, Clone, Hash, Eq)]
+#[logos(extras = (usize, usize))]
+#[logos(skip r"[ \t\r\f]+")]
+#[logos(skip r"#[^\n]*")]
+#[regex(r"\n", newline_callback)]
+pub enum Token {
+    #[allow(dead_code)]
+    Error,
+
+    #[regex(r"[a-zA-Z_][a-zA-Z0-9_]*", callback = |lex| lex.slice().to_string())]
+    Identifier(String),
+
+    // Float stored as raw bits — f64 doesn't implement Hash/Eq.
+    // Reconstruct with f64::from_bits(bits).
+    #[regex(r"-?[0-9]+\.[0-9]+", callback = |lex| lex.slice().parse::<f64>().unwrap().to_bits())]
+    Float(u64),
+
+    #[regex(r"-?[0-9]+", callback = |lex| lex.slice().parse::<i32>().unwrap())]
+    Integer(i32),
+
+    #[regex("\"([^\"\\\\]|\\\\.)*\"", callback = |lex| lex.slice().to_string())]
+    String(String),
+
+    #[token("=")]
+    Equal,
+
+    #[token(",")]
+    Comma,
+
+    #[token("(")]
+    LeftParen,
+
+    #[token(")")]
+    RightParen,
+
+    #[regex(r"\n", newline_callback)]
+    Newline,
+}
+
+/// Logos callback invoked on every newline character.
+///
+/// Increments the line counter (`extras.0`) and records the byte offset of
+/// the start of the new line (`extras.1`). Returns `Skip` so the newline
+/// token is not emitted into the token stream.
+fn newline_callback(lex: &mut Lexer<Token>) -> Skip {
+    lex.extras.0 += 1;
+    lex.extras.1 = lex.span().start + 1;
+    Skip
+}
+
+impl fmt::Display for Token {
+    /// Formats a token as the original source text it was produced from.
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Token::Error => write!(f, "Error"),
+            Token::Identifier(id) => write!(f, "{}", id),
+            Token::Float(bits) => write!(f, "{}", f64::from_bits(*bits)),
+            Token::Integer(i) => write!(f, "{}", i),
+            Token::String(s) => write!(f, "{}", s),
+            Token::Equal => write!(f, "="),
+            Token::Comma => write!(f, ","),
+            Token::LeftParen => write!(f, "("),
+            Token::RightParen => write!(f, ")"),
+            Token::Newline => writeln!(f),
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use logos::Logos;
+    use std::fs;
+    use std::path::Path;
+
+    /// Smoke-tests the lexer on a small inline BIMR program,
+    /// verifying that it produces a non-empty token stream starting with
+    /// an identifier followed by `=`.
+    #[test]
+    fn test_lexer_simple() {
+        let input = r#"p1 = Point(0,0,0)
+p2 = Point(500,0,0)
+l1 = Line(p1,p2)
+v1 = Normal(l1,"up")
+v2 = Vector(0,0,250)
+f1 = Extrude(l1,v1)
+v1 = Extrude(f1,v2)
+w1 = Wall(v1)"#;
+
+        let mut lexer = Token::lexer(input);
+        let mut tokens = Vec::new();
+        for token in lexer.by_ref() {
+            match token {
+                Ok(t) => tokens.push(t),
+                Err(_) => panic!("Lexer error"),
+            }
+        }
+
+        // Basic checks
+        assert!(!tokens.is_empty());
+        assert!(matches!(tokens[0], Token::Identifier(_)));
+        assert!(matches!(tokens[1], Token::Equal));
+        // More detailed checks can be added
+    }
+
+    /// Verifies that `#` line comments are silently skipped, whether they
+    /// appear on their own line or trailing after code.
+    #[test]
+    fn test_lexer_skips_line_comments() {
+        let input = r#"# a full-line comment
+p1 = Point(0,0,0) # trailing comment"#;
+        let tokens = Token::lexer(input)
+            .filter_map(Result::ok)
+            .collect::<Vec<_>>();
+        assert!(tokens.iter().all(|t| !matches!(t, Token::Error)));
+        assert_eq!(tokens[0], Token::Identifier("p1".to_string()));
+        assert!(tokens.contains(&Token::Identifier("Point".to_string())));
+        assert!(tokens.len() < 20, "comment text leaked into token stream");
+    }
+
+    /// Verifies that a `#` inside a string literal is not treated as a
+    /// comment start.
+    #[test]
+    fn test_lexer_hash_inside_string_is_not_comment() {
+        let input = r#"x = "a#b""#;
+        let tokens = Token::lexer(input)
+            .filter_map(Result::ok)
+            .collect::<Vec<_>>();
+        assert!(
+            tokens.contains(&Token::String(r#""a#b""#.to_string())),
+            "expected the full string token, got {:?}",
+            tokens
+        );
+    }
+
+    /// Runs the lexer over every `.bimr` file in the `samples/` directory
+    /// and asserts that no lex errors occur, printing the offending line and
+    /// column when one does.
+    #[test]
+    #[allow(clippy::while_let_on_iterator)]
+    fn test_lexer_on_bimr_files() {
+        let folder_path = "../samples";
+        assert!(Path::new(folder_path).exists());
+
+        for f in fs::read_dir(folder_path).unwrap() {
+            let entry = f.unwrap();
+            let p = entry.path();
+            if p.extension()
+                .map(|ext| ext.to_str() == Some("bimr"))
+                .unwrap_or(false)
+            {
+                println!("Lexing file: {:?}", p);
+                let input = fs::read_to_string(&p).expect("Failed to read file");
+
+                let mut lexer = Token::lexer(&input);
+                while let Some(token) = lexer.next() {
+                    let span = lexer.span();
+                    match token {
+                        Ok(_) => {}
+                        Err(_) => {
+                            let line = lexer.extras.0;
+                            panic!(
+                                "error lexing {:?}: '{:?}' at {:?} on line {}\n\n{}\n\n",
+                                p,
+                                &input[span.clone()],
+                                span,
+                                line,
+                                input.lines().nth(line).unwrap()
+                            );
+                        }
+                    }
+                }
+            }
+        }
+    }
+}

lexer/src/lib.rs

@@ -0,0 +1,6 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+pub mod lexer;
+
+pub use crate::lexer::Token;

lexer/src/main.rs

@@ -0,0 +1,130 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+mod lexer;
+
+use clap::Parser;
+use lexer::Token;
+use logos::Logos;
+use std::fs;
+use std::path::Path;
+
+#[derive(Parser)]
+#[command(name = "bimr-lexer")]
+#[command(about = "A lexer for BIMR DSL")]
+#[command(version)]
+struct Args {
+    /// Input BIMR (.bimr) file to lex
+    #[arg(value_name = "FILE|DIRECTORY")]
+    file: String,
+
+    /// Print verbose output including all tokens
+    #[arg(short, long)]
+    verbose: bool,
+}
+
+/// Lexes a single `.bimr` file and reports any errors to stderr.
+///
+/// When `verbose` is true, every token is printed to stdout along with its
+/// byte span and source text, and a success/failure summary is printed at the
+/// end.
+fn lex_file(file_path: &Path, verbose: bool) {
+    if verbose {
+        println!("Lexing file: {}", file_path.display());
+    }
+    let input = fs::read_to_string(file_path).expect("Failed to read file");
+
+    let mut lexer = Token::lexer(&input);
+    let mut success = true;
+
+    while let Some(token) = lexer.next() {
+        let span = lexer.span();
+        match token {
+            Ok(t) => {
+                if verbose {
+                    println!(
+                        "Token: {:?}, Span: {:?}, Text: '{}'",
+                        t,
+                        span,
+                        &input[span.clone()]
+                    );
+                }
+            }
+            Err(_) => {
+                success = false;
+
+                let line_num = lexer.extras.0;
+                let line_start = lexer.extras.1;
+
+                let line_text = input.lines().nth(line_num).unwrap_or("");
+                let col_start = span.start - line_start;
+                let col_end = span.end - line_start;
+
+                let mut visual_col = 0;
+                for (i, ch) in line_text.char_indices() {
+                    if i >= col_start {
+                        break;
+                    }
+                    if ch == '\t' {
+                        visual_col += 8 - (visual_col % 8);
+                    } else {
+                        visual_col += 1;
+                    }
+                }
+
+                let indicator = " ".repeat(visual_col) + &"^".repeat((col_end - col_start).max(1));
+
+                eprintln!(
+                    "Error lexing '{}': '{}' at {:?} on line {} column {}\n\n{}\n{}\n",
+                    file_path.display(),
+                    &input[span.clone()],
+                    span,
+                    line_num + 1,
+                    col_start + 1,
+                    line_text,
+                    indicator
+                );
+            }
+        }
+    }
+
+    if verbose {
+        if success {
+            println!("✓ Successfully lexed '{}'", file_path.display());
+        } else {
+            println!("✗ Failed to lex '{}'", file_path.display());
+        }
+    }
+}
+
+/// Entry point for the `bimr-lexer` CLI tool.
+///
+/// Accepts a single file path or a directory. When a directory is given, every
+/// `.bimr` file it contains is lexed in turn.
+fn main() {
+    let args = Args::parse();
+    let path = Path::new(&args.file);
+
+    if !path.exists() {
+        eprintln!("Error: file or directory '{}' not found", args.file);
+        return;
+    }
+
+    if path.is_dir() {
+        if args.verbose {
+            println!("Lexing all .bimr files in directory: {}", args.file);
+        }
+        for entry in fs::read_dir(path).expect("Failed to read directory") {
+            let entry = entry.expect("Failed to read directory entry");
+            let file_path = entry.path();
+            if file_path.is_file()
+                && let Some(ext) = file_path.extension()
+                && ext == "bimr"
+            {
+                lex_file(&file_path, args.verbose);
+            }
+        }
+    } else {
+        lex_file(path, args.verbose);
+    }
+}

parser/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "parser"
+version = "0.0.1"
+edition = "2024"
+
+[dependencies]
+chumsky = "0.10.0"
+logos = "0.15"
+lexer = { path = "../lexer" }
+
+[lib]
+name = "parser"
+path = "src/lib.rs"
+
+[[bin]]
+name = "bimr-parser"
+path = "src/main.rs"

parser/src/ast.rs

@@ -0,0 +1,60 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+/// Root AST node. A BIMR program is an ordered sequence of statements.
+#[derive(Debug, Clone)]
+pub struct Program {
+    pub statements: Vec<Statement>,
+}
+
+/// A single statement. Every statement in the BIMR DSL is an assignment.
+#[derive(Debug, Clone)]
+pub struct Statement {
+    pub assignment: Assignment,
+}
+
+/// An assignment binds the result of an expression to a named identifier.
+/// Example: `w1 = Wall(l1, thickness=200, height=3000)`
+#[derive(Debug, Clone)]
+pub struct Assignment {
+    pub identifier: String,
+    pub expression: Expression,
+}
+
+/// An expression on the right-hand side of an assignment.
+///
+/// The BIMR DSL supports function calls, bare identifier references (variable
+/// lookups), numeric literals, string literals, and inline tuples used as
+/// positional point arguments inside `List(…)` calls.
+#[derive(Debug, Clone)]
+pub enum Expression {
+    FunctionCall(FunctionCall),
+    Identifier(String),
+    Integer(i32),
+    Float(f64),
+    String(String),
+    /// Inline tuple `(a, b)` or `(a, b, c)` — used for point literals inside
+    /// `List(…)` arguments. Requires at least two elements.
+    Tuple(Vec<Expression>),
+}
+
+/// A function argument — either positional or keyword.
+///
+/// Example positional: `Wall(l1, 200, 3000)` → three `Positional` args.
+/// Example keyword:    `Wall(l1, thickness=200)` → one `Keyword` arg.
+#[derive(Debug, Clone)]
+pub enum Argument {
+    Positional(Expression),
+    Keyword(String, Expression),
+}
+
+/// A function call expression: a name followed by a parenthesised argument list.
+///
+/// All built-in BIMR constructors (`Point`, `Wall`, `Each`, …) and generative
+/// operators are represented as `FunctionCall` nodes. Dispatch to the correct
+/// `eval_call` arm happens in the evaluator by matching on `name`.
+#[derive(Debug, Clone)]
+pub struct FunctionCall {
+    pub name: String,
+    pub arguments: Vec<Argument>,
+}

parser/src/lib.rs

@@ -0,0 +1,7 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+pub mod ast;
+pub mod parser;
+
+pub use parser::parse;

parser/src/main.rs

@@ -0,0 +1,28 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+use std::fs;
+
+/// Entry point for the `bimr-parser` CLI tool.
+///
+/// Reads a `.bimr` source file given as the first command-line argument,
+/// parses it, and prints the resulting AST (on success) or the list of parse
+/// errors (on failure).
+fn main() -> Result<(), std::io::Error> {
+    let file_path = std::env::args().nth(1).unwrap();
+    let src = fs::read_to_string(&file_path).unwrap();
+
+    match parser::parse(&src) {
+        Ok(parsed) => {
+            println!("Parsed successfully!");
+            println!("AST: {:#?}", parsed);
+        }
+        Err(errors) => {
+            for error in errors {
+                println!("Error: {:?}", error);
+            }
+        }
+    }
+
+    Ok(())
+}

parser/src/parser.rs

@@ -0,0 +1,298 @@
+// SPDX-FileCopyrightText: 2026 Milovann Yanatchkov
+// SPDX-License-Identifier: MIT
+
+use crate::ast::*;
+use chumsky::prelude::*;
+use chumsky::{input::Stream, input::ValueInput};
+use lexer::Token;
+use logos::Logos;
+
+/// Parses a BIMR DSL source string into a `Program` AST.
+///
+/// Lexes `input` with `logos`, wraps the token iterator in a `chumsky`
+/// `Stream`, and runs the `program` combinator. Returns the AST on success or
+/// a list of `Simple` parse errors on failure.
+pub fn parse(input: &str) -> Result<Program, Vec<Simple<'_, Token>>> {
+    let token_iter = Token::lexer(input).spanned().map(|(tok, span)| match tok {
+        Ok(tok) => (tok, SimpleSpan::from(span)),
+        Err(()) => (Token::Error, span.into()),
+    });
+
+    let token_stream = Stream::from_iter(token_iter).map((0..input.len()).into(), |(t, s)| (t, s));
+
+    program().parse(token_stream).into_result()
+}
+
+/// Parser combinator for a complete BIMR program.
+///
+/// A program is zero or more `statement`s collected into a `Program` node.
+fn program<'tokens, I>() -> impl Parser<'tokens, I, Program, extra::Err<Simple<'tokens, Token>>>
+where
+    I: ValueInput<'tokens, Token = Token, Span = SimpleSpan>,
+{
+    statement()
+        .repeated()
+        .collect()
+        .map(|statements| Program { statements })
+}
+
+/// Parser combinator for a single assignment statement.
+///
+/// Grammar: `identifier = expression`
+fn statement<'tokens, I>() -> impl Parser<'tokens, I, Statement, extra::Err<Simple<'tokens, Token>>>
+where
+    I: ValueInput<'tokens, Token = Token, Span = SimpleSpan>,
+{
+    identifier()
+        .then_ignore(just(Token::Equal))
+        .then(expression())
+        .map(|(identifier, expression)| Statement {
+            assignment: Assignment {
+                identifier,
+                expression,
+            },
+        })
+}
+
+/// Parser combinator for an expression (RHS of an assignment).
+///
+/// Tries, in order: function call, tuple, bare atom (identifier / number /
+/// string). Function calls are tried first to avoid mis-parsing `Name(…)` as
+/// a bare identifier followed by junk.
+fn expression<'tokens, I>()
+-> impl Parser<'tokens, I, Expression, extra::Err<Simple<'tokens, Token>>>
+where
+    I: ValueInput<'tokens, Token = Token, Span = SimpleSpan>,
+{
+    // Atomic expressions — no tuple here to avoid ambiguity with function call parens.
+    let atom = || {
+        choice((
+            identifier().map(Expression::Identifier),
+            select! { Token::Float(bits) => Expression::Float(f64::from_bits(bits)) },
+            select! { Token::Integer(i) => Expression::Integer(i) },
+            select! { Token::String(s) => Expression::String(s) },
+        ))
+    };
+
+    // Tuple: (expr, expr) or (expr, expr, expr) — at least two elements.
+    // Used for inline point literals inside List(...) args.
+    // Constructed as a closure so it can be used in multiple places without Clone.
+    let tuple = || {
+        atom()
+            .separated_by(just(Token::Comma))
+            .at_least(2)
+            .collect::<Vec<_>>()
+            .delimited_by(just(Token::LeftParen), just(Token::RightParen))
+            .map(Expression::Tuple)
+    };
+
+    // A single argument: either `ident=expr` (keyword) or `expr` (positional).
+    // atom() is used as the value expression to keep things non-recursive.
+    let argument = identifier()
+        .then_ignore(just(Token::Equal))
+        .then(atom())
+        .map(|(key, val)| Argument::Keyword(key, val))
+        .or(choice((tuple(), atom())).map(Argument::Positional));
+
+    // Function call: Identifier(arg, ...)
+    let function_call = identifier()
+        .then(
+            argument
+                .separated_by(just(Token::Comma))
+                .allow_trailing()
+                .collect::<Vec<_>>()
+                .delimited_by(just(Token::LeftParen), just(Token::RightParen)),
+        )
+        .map(|(name, arguments)| Expression::FunctionCall(FunctionCall { name, arguments }));
+
+    choice((function_call, tuple(), atom()))
+}
+
+/// Parser combinator that matches a single `Token::Identifier` and returns
+/// its string value.
+fn identifier<'tokens, I>() -> impl Parser<'tokens, I, String, extra::Err<Simple<'tokens, Token>>>
+where
+    I: ValueInput<'tokens, Token = Token, Span = SimpleSpan>,
+{
+    select! { Token::Identifier(s) => s }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn parse_one(src: &str) -> Program {
+        parse(src).expect("parse failed")
+    }
+
+    // ── Basic assignments ─────────────────────────────────────────────────────
+
+    #[test]
+    fn test_parse_integer() {
+        let prog = parse_one("x = 42");
+        assert_eq!(prog.statements.len(), 1);
+        let stmt = &prog.statements[0].assignment;
+        assert_eq!(stmt.identifier, "x");
+        assert!(matches!(stmt.expression, Expression::Integer(42)));
+    }
+
+    #[test]
+    #[allow(clippy::approx_constant)]
+    fn test_parse_float() {
+        let prog = parse_one("x = 3.14");
+        let expr = &prog.statements[0].assignment.expression;
+        assert!(matches!(expr, Expression::Float(v) if (v - 3.14).abs() < 1e-10));
+    }
+
+    #[test]
+    fn test_parse_negative_int() {
+        let prog = parse_one("x = -7");
+        let expr = &prog.statements[0].assignment.expression;
+        assert!(matches!(expr, Expression::Integer(-7)));
+    }
+
+    #[test]
+    fn test_parse_string() {
+        // The lexer preserves the surrounding quotes in the token value.
+        let prog = parse_one(r#"x = "hello""#);
+        let expr = &prog.statements[0].assignment.expression;
+        assert!(matches!(expr, Expression::String(s) if s == r#""hello""#));
+    }
+
+    #[test]
+    fn test_parse_identifier() {
+        let prog = parse_one("x = y");
+        let expr = &prog.statements[0].assignment.expression;
+        assert!(matches!(expr, Expression::Identifier(id) if id == "y"));
+    }
+
+    // ── Function calls ────────────────────────────────────────────────────────
+
+    #[test]
+    fn test_parse_point() {
+        let prog = parse_one("p1 = Point(0, 0, 0)");
+        let expr = &prog.statements[0].assignment.expression;
+        if let Expression::FunctionCall(fc) = expr {
+            assert_eq!(fc.name, "Point");
+            assert_eq!(fc.arguments.len(), 3);
+        } else {
+            panic!("expected FunctionCall");
+        }
+    }
+
+    #[test]
+    fn test_parse_line() {
+        let prog = parse_one("l1 = Line(p1, p2)");
+        let expr = &prog.statements[0].assignment.expression;
+        if let Expression::FunctionCall(fc) = expr {
+            assert_eq!(fc.name, "Line");
+            assert_eq!(fc.arguments.len(), 2);
+        } else {
+            panic!("expected FunctionCall");
+        }
+    }
+
+    #[test]
+    fn test_parse_wall_with_keywords() {
+        let prog = parse_one("w1 = Wall(l1, thickness=200, height=3000)");
+        let expr = &prog.statements[0].assignment.expression;
+        if let Expression::FunctionCall(fc) = expr {
+            assert_eq!(fc.name, "Wall");
+            assert_eq!(fc.arguments.len(), 3);
+            assert!(matches!(&fc.arguments[0], Argument::Positional(_)));
+            assert!(matches!(&fc.arguments[1], Argument::Keyword(k, _) if k == "thickness"));
+            assert!(matches!(&fc.arguments[2], Argument::Keyword(k, _) if k == "height"));
+        } else {
+            panic!("expected FunctionCall");
+        }
+    }
+
+    #[test]
+    fn test_parse_each_operator() {
+        let src = r#"e1 = Each(div, "Frame", fw=200, height=300, tangent="auto")"#;
+        let prog = parse_one(src);
+        let expr = &prog.statements[0].assignment.expression;
+        if let Expression::FunctionCall(fc) = expr {
+            assert_eq!(fc.name, "Each");
+            assert!(fc.arguments.len() >= 2);
+        } else {
+            panic!("expected FunctionCall");
+        }
+    }
+
+    // ── Multiple statements ───────────────────────────────────────────────────
+
+    #[test]
+    fn test_parse_multiple_statements() {
+        let src = "p1 = Point(0, 0, 0)\np2 = Point(100, 0, 0)\nl1 = Line(p1, p2)";
+        let prog = parse_one(src);
+        assert_eq!(prog.statements.len(), 3);
+    }
+
+    #[test]
+    fn test_parse_empty_program() {
+        let prog = parse_one("");
+        assert!(prog.statements.is_empty());
+    }
+
+    // ── Inline tuples ─────────────────────────────────────────────────────────
+
+    #[test]
+    fn test_parse_tuple_in_list() {
+        let src = "lst = List((0, 0, 0), (100, 0, 0))";
+        let prog = parse_one(src);
+        let expr = &prog.statements[0].assignment.expression;
+        if let Expression::FunctionCall(fc) = expr {
+            assert_eq!(fc.name, "List");
+            assert_eq!(fc.arguments.len(), 2);
+            for arg in &fc.arguments {
+                assert!(matches!(arg, Argument::Positional(Expression::Tuple(_))));
+            }
+        } else {
+            panic!("expected FunctionCall");
+        }
+    }
+
+    // ── Comments ──────────────────────────────────────────────────────────────
+
+    #[test]
+    fn test_parse_with_comments() {
+        let src =
+            "# a full-line comment\np1 = Point(0, 0, 0) # trailing comment\nl1 = Line(p1, p1)";
+        let prog = parse_one(src);
+        assert_eq!(prog.statements.len(), 2);
+    }
+
+    #[test]
+    fn test_parse_comment_before_statement() {
+        let prog = parse_one("# nothing here yet\nx = 42");
+        assert_eq!(prog.statements.len(), 1);
+        assert_eq!(prog.statements[0].assignment.identifier, "x");
+    }
+
+    // ── Error handling ────────────────────────────────────────────────────────
+
+    #[test]
+    fn test_parse_error_missing_paren() {
+        let result = parse("p1 = Point(0, 0");
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_parse_error_unclosed_string() {
+        let result = parse(r#"x = "hello"#);
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_parse_error_bad_syntax() {
+        let result = parse("= 42");
+        assert!(result.is_err());
+    }
+
+    #[test]
+    fn test_parse_error_unknown_token() {
+        let result = parse("x = @@@");
+        assert!(result.is_err());
+    }
+}

samples/bimr/column_grid.bimr

@@ -0,0 +1,18 @@
+p1 = Point(0,0,0)
+p2 = Point(0,1000,0)
+p3 = Point(0,2000,0)
+p4 = Point(0,3000,0)
+p5 = Point(1000,0,0)
+p6 = Point(1000,1000,0)
+p7 = Point(1000,2000,0)
+p8 = Point(1000,3000,0)
+p9 = Point(2000,0,0)
+p10 = Point(2000,1000,0)
+p11 = Point(2000,2000,0)
+p12 = Point(2000,3000,0)
+p13 = Point(3000,0,0)
+p14 = Point(3000,1000,0)
+p15 = Point(3000,2000,0)
+p16 = Point(3000,3000,0)
+lst = List(p1, p2, p3, p4, p5, p6, p7, p8, p9, p10, p11, p12, p13, p14, p15, p16)
+cols = Column(lst,300,30,30)

samples/bimr/wall.bimr

@@ -0,0 +1,4 @@
+p1 = Point(0,0,0)
+p2 = Point(500,0,0)
+l1 = Line(p1,p2)
+w1 = Wall(l1,20,300)

samples/bimr/wall.ifcx

@@ -0,0 +1,181 @@
+{
+  "data": [
+    {
+      "attributes": {
+        "usd::usdgeom::mesh": {
+          "faceVertexIndices": [
+            0,
+            1,
+            2,
+            0,
+            2,
+            3,
+            4,
+            5,
+            6,
+            4,
+            6,
+            7,
+            8,
+            9,
+            10,
+            8,
+            10,
+            11,
+            12,
+            13,
+            14,
+            12,
+            14,
+            15,
+            16,
+            17,
+            18,
+            16,
+            18,
+            19,
+            20,
+            21,
+            22,
+            20,
+            22,
+            23
+          ],
+          "points": [
+            [
+              0.0,
+              0.0,
+              0.0
+            ],
+            [
+              0.0,
+              -20.0,
+              0.0
+            ],
+            [
+              500.0,
+              -20.0,
+              0.0
+            ],
+            [
+              500.0,
+              0.0,
+              0.0
+            ],
+            [
+              0.0,
+              0.0,
+              300.0
+            ],
+            [
+              500.0,
+              0.0,
+              300.0
+            ],
+            [
+              500.0,
+              -20.0,
+              300.0
+            ],
+            [
+              0.0,
+              -20.0,
+              300.0
+            ],
+            [
+              0.0,
+              0.0,
+              0.0
+            ],
+            [
+              500.0,
+              0.0,
+              0.0
+            ],
+            [
+              500.0,
+              0.0,
+              300.0
+            ],
+            [
+              0.0,
+              0.0,
+              300.0
+            ],
+            [
+              0.0,
+              -20.0,
+              0.0
+            ],
+            [
+              0.0,
+              -20.0,
+              300.0
+            ],
+            [
+              500.0,
+              -20.0,
+              300.0
+            ],
+            [
+              500.0,
+              -20.0,
+              0.0
+            ],
+            [
+              0.0,
+              0.0,
+              0.0
+            ],
+            [
+              0.0,
+              0.0,
+              300.0
+            ],
+            [
+              0.0,
+              -20.0,
+              300.0
+            ],
+            [
+              0.0,
+              -20.0,
+              0.0
+            ],
+            [
+              500.0,
+              0.0,
+              0.0
+            ],
+            [
+              500.0,
+              -20.0,
+              0.0
+            ],
+            [
+              500.0,
+              -20.0,
+              300.0
+            ],
+            [
+              500.0,
+              0.0,
+              300.0
+            ]
+          ]
+        }
+      },
+      "path": "wall-001"
+    }
+  ],
+  "header": {
+    "dataVersion": "1.0.0",
+    "ifcxVersion": "ifcx_alpha"
+  },
+  "imports": [
+    {
+      "uri": "https://ifcx.dev/@openusd.org/usd@v1.ifcx"
+    }
+  ],
+  "schemas": {}
+}

samples/bimr/wall_v2.bimr

@@ -0,0 +1,8 @@
+p1 = Point(0,0,0)
+p2 = Point(800,0,0)
+l1 = Line(p1,p2)
+w1 = Wall(l1,20,300)
+p3 = Point(0,1000,0)
+p4 = Point(800,1000,0)
+l2 = Line(p3,p4)
+w2 = Wall(l2,20,300)

samples/python/building.py

@@ -0,0 +1,30 @@
+# Welcome to BIMR.NET!
+# This is a live editor, try tweaking this Python example
+
+N_STOREYS = 8
+N_SEGMENTS = 50
+FRAME_W, FRAME_H, FRAME_D, FRAME_T = 200, 180, 35, 10
+SLAB_T = 150
+STOREY_H = FRAME_H + 2 * SLAB_T
+
+BASE = [
+    (-1500, -300),
+    (0, 1000),
+    (850, 800),
+    (300, 0),
+    (500, -800),
+    (0, -1000),
+    (-500, -800),
+    (-300, 0),
+]
+
+for storey in range(N_STOREYS):
+    z = storey * STOREY_H
+    base = List(*[Point(x, y, z) for x, y in BASE])
+    pts = Random(base, seed=128 + storey, min=-150, max=150, dims=2)
+    curve = Curve(pts)
+    s_down = Slab(curve, SLAB_T, z)
+    s_up = Slab(curve, SLAB_T, z + SLAB_T + FRAME_H)
+    segments = Cut(curve, N_SEGMENTS)
+    pairs = Explode(segments)
+    frames = Frame(pairs, FRAME_W, FRAME_H, FRAME_D, FRAME_T)

samples/python/cylinders.py

@@ -0,0 +1,12 @@
+# cylinders.py
+
+def cylinder(x,y,z,r,h):
+    center = Point(x, y, z)
+    circle = Circle(center, r)
+    segments = Cut(circle, 12)
+    pairs = Explode(segments)
+    frames = Frame(pairs, 100, h, 60, 60)
+
+cylinder(0,0,0,1000,300)
+cylinder(-200,200,0,500,600)
+cylinder(-1800,-1000,0,500,600)

samples/python/grid.py

@@ -0,0 +1,5 @@
+# grid.py
+
+pts = [Point(x * -100, y * -100, 0) for x in range(40) for y in range(40)]
+grid = List(*pts)
+cols = Column(grid, 300, 30, 30)