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Lean 4 fork for HoTT-compatible kernel extensions (Path types, transport, HITs). Maintained against upstream leanprover/lean4.
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Leonardo de Moura 175661b6c3
refactor: reorganize SymM and GrindM monad hierarchy (#11909) 
This PR reorganizes the monad hierarchy for symbolic computation in
Lean.

## Motivation

We want a clean layering where:
1. A foundational monad (`SymM`) provides maximally shared terms and
structural/syntactic `isDefEq`
2. `GrindM` builds on this foundation, adding E-graphs, congruence
closure, and decision procedures
3. Symbolic execution / VCGen uses `GrindM` directly without introducing
a third monad

## Changes

The core symbolic computation layer still lives in `Lean.Meta.Sym`. This
monad (`SymM`) provides:
- Maximally shared terms with pointer-based equality
- Structural/syntactic `isDefEq` and matching (no reduction, predictable
cost)
- Monotonic local contexts (no `revert` or `clear`), enabling O(1)
metavariable validation
- Efficient `intro`, `apply`, and `simp` implementations

The name "Sym" reflects that this is infrastructure for symbolic
computation: symbolic simulation, verification condition generation, and
decision procedures.

### Updated hierarchy

```
Lean.Meta.Sym   -- SymM: shared terms, syntactic isDefEq, intro, apply, simp
Lean.Meta.Grind -- GrindM: E-graphs, congruence closure (extends SymM)
```

Symbolic execution is a usage pattern of `GrindM` operating on
`Grind.Goal`, not a separate monad. This keeps the API surface minimal:
users learn two monads, and VCGen is "how you use `GrindM`" (for users
that want to use `grind`) rather than a third abstraction to understand.
2026-01-06 01:12:07 +00:00
.claude doc: expand PR creation guidelines in CLAUDE.md (#11835) 2025-12-29 17:42:28 +00:00
.github fix: remove batteries tag check from PR mathlib CI (#11707) 2025-12-17 08:53:04 +00:00
doc doc: replace ffi.md with links to the reference manual (#11737) 2025-12-19 07:23:06 +00:00
images
releases_drafts chore: add release draft for the module system (#11359) 2025-11-26 15:01:07 +00:00
script chore: include comparator and lean4export in release process (#11899) 2026-01-05 01:08:50 +00:00
src refactor: reorganize SymM and GrindM monad hierarchy (#11909) 2026-01-06 01:12:07 +00:00
stage0 chore: update stage0 2025-12-27 03:18:33 +00:00
tests refactor: reorganize SymM and GrindM monad hierarchy (#11909) 2026-01-06 01:12:07 +00:00
.gitattributes doc: grove: update and add String data (#11551) 2025-12-08 16:49:37 +00:00
.gitignore chore: add .vscode/settings.json to .gitignore (#10795) 2025-10-16 07:08:41 +00:00
.gitpod.Dockerfile
.gitpod.yml
.ignore
CMakeLists.txt fix: cadical dynamic dependencies (#11475) 2025-12-02 13:54:26 +00:00
CMakePresets.json chore: CI: enable leak sanitizer again (#11339) 2025-11-27 18:32:35 +00:00
CODEOWNERS chore: make @hargoniX code owner of the compiler (#10732) 2025-10-10 04:43:38 +00:00
CONTRIBUTING.md
flake.lock chore: robustify Nix shell (#8141) 2025-04-28 15:08:32 +00:00
flake.nix chore: use lld if available for building core (#10694) 2025-10-08 16:47:30 +00:00
lean-toolchain
lean.code-workspace chore: lean.code-workspace: fix terminal cwd (#10802) 2025-10-16 20:19:12 +00:00
LICENSE
LICENSES
README.md doc: update URLs that are currently pointing to redirects (#10397) 2025-09-17 15:50:07 +00:00
RELEASES.md

README.md

This is the repository for Lean 4.

About

Installation

See Install Lean.

Contributing

Please read our Contribution Guidelines first.

Building from Source

See Building Lean.