cubical-transport-hott-lean4/CubicalTransport/FFI.lean
Maximus Gorog 31d19f655e
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Split: engine = cubical-transport HoTT only
Restructure to engine-only contents.  Application code (Topolei.*
namespace, canvas-rs / render Rust crates, Main / ProbeTest, naga IR
pipeline, Selection / Subobject / Trace / Obs.Ctx hypothesis stack,
cells-spec / HYPOTHESES / STATUS / NAGA_IR_PLAN docs) moves to the
sibling repo max/topolei.

What moved:
- `Topolei/Cubical/*.lean` (22 files) → `CubicalTransport/*.lean`
  with namespace `Topolei.Cubical.*` renamed to `CubicalTransport.*`.
  Fully-qualified test types `TopoleiCubical{FFI,Property}Test` →
  `CubicalTransport{FFI,Property}Test` for consistency.
- New root file `CubicalTransport.lean` re-exporting all 22 modules.
- Lakefile: package `cubicalTransport`; lib `CubicalTransport`; only
  `cubical-test` and `cubical-bench` exes (no GPU link path).

The split criterion: anything an AI shortcut could break that would
cascade-corrupt downstream proofs lives here.  Anything that would
only break the application stays in the topolei interface repo.

cubical-test passes 62/62 (smoke + properties) on the renamed engine.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
2026-04-27 21:35:01 -06:00

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2.6 KiB
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/-
Topolei.Cubical.FFI
===================
Documentation + convenience re-exports for the Rust cubical-HoTT
backend (Phase C, 2026-04-24).
## Architecture after Phase C
The `@[extern "topolei_cubical_*"]` `opaque` declarations and their
`@[implemented_by]` attributes are **inlined directly in the files
that own the fallback `partial def`**:
| Function | File where extern + impl_by live |
|-----------------------|----------------------------------|
| `eval` | `Cubical/Eval.lean` |
| `vApp`, `vPApp` | `Cubical/Eval.lean` |
| `vHCompValue` | `Cubical/Eval.lean` |
| `vCompAtTerm` | `Cubical/Eval.lean` |
| `vCompNAtTerm` | `Cubical/Eval.lean` |
| `vFst`, `vSnd` | `Cubical/Eval.lean` |
| `vTransp` | `Cubical/Transport.lean` |
| `readback` | `Cubical/Readback.lean` |
| `readbackNeu` | `Cubical/Readback.lean` |
| `DimExpr.normalize` | `Cubical/Interval.lean` |
| `FaceFormula.normalize` | `Cubical/Face.lean` |
**Why inline.** Lean 4 requires `@[implemented_by]` to be attached
at the declaration site. A central FFI module that tries to
retroactively attach the attribute to imported declarations fails
with `Cannot add attribute [implemented_by] to declaration ... in
an imported module`. The extern declaration and the `partial def`
must therefore be co-located.
This file is kept as a documentation anchor + a place to add any
future shared FFI utilities that don't belong to a specific
cubical-core module.
## Runtime behaviour
When `libtopolei_cubical.a` is linked (default via `lakefile.toml`),
every runtime call to `eval` / `vApp` / `readback` / etc. routes
through Rust at native speed. Kernel-level proof reasoning
continues to go through the axioms in each module — unchanged.
Without the Rust library linked, compilation fails at link time
(every extern symbol is unresolved), so a built executable always
has Rust present.
## ABI version
`TOPOLEI_FFI_ABI_VERSION = 1`. Defined in
`native/cubical/include/topolei_cubical.h`. Any change to an
`@[extern]` signature (arity, argument types) requires incrementing
the version and updating the C header.
## Related documents
- `FFI_DESIGN.md` — C ABI contract (memory, marshalling, ownership).
- `FFI_COMPLETENESS.md` — per-function axiom-coverage audit.
- `KERNEL_BOUNDARY.md` — what this delivers vs. what requires kernel work.
-/
import CubicalTransport.Readback