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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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Tom Levy e42892cfb6
doc: fix comment about String.fromUTF8 replacing invalid chars (#10240) 
Hi, the doc of `String.fromUTF8` previously said invalid characters are
replaced with 'A'. But the parameter `h : validateUTF8 a` guarantees
there are no invalid characters, so that explanation doesn't make sense
to me. This PR deletes that explanation (and fixes some unrelated
typos).

I also have a patch that uses `h` to prove each of the characters is
valid, eliminating the need for a default character
([pr/chore-String-fromUTF8-prove-valid](27f1ff36b2)),
would you be interested in merging that?

<details>
<summary>Notes on invalid characters from unchecked C++</summary>
I don't know if this function may be called from unchecked C++ with
invalid characters. If it may, I'm not sure what would happen with my
patched function... I'm not familiar with Lean's safety model, but it
seems like a bad idea to have a Lean function that takes a proof of a
proposition but is expected to operate in a certain way even if the
proposition is false. I think the safe approach is to have two functions
-- one that takes a proof and is only called from Lean, and another that
doesn't take a proof and replaces invalid chars (for use from C++, not
sure whether it's useful from Lean); I'd prefer to go even further and
report an error instead of silently replacing invalid characters (I'm
not sure if there is any easy way to report errors/panic in Lean code
called from C++).
</details>
2025-09-23 10:19:20 +00:00
.github chore: CI: ensure cache reuse in update-stage0 (#10359) 2025-09-12 14:56:32 +00:00
doc doc: testing Lean while avoiding rebuilds for downstream projects (#10328) 2025-09-10 13:53:34 +00:00
images chore(CMakeLists.txt): move Lean logo to make sure we can test leanemacs without installing Lean 2015-01-31 17:38:49 -08:00
releases_drafts chore: updates to release_checklist.md (#7817) 2025-04-04 03:45:36 +00:00
script chore: include lean-lang.org in release checklist (#10450) 2025-09-19 03:46:32 +00:00
src doc: fix comment about String.fromUTF8 replacing invalid chars (#10240) 2025-09-23 10:19:20 +00:00
stage0 chore: update stage0 2025-09-23 06:22:49 +00:00
tests fix: Use @[tactic_alt] for bv_decide, mvcgen and similar tactics (#10506) 2025-09-23 07:40:02 +00:00
.gitattributes fix: mark doc parser tests as eol=lf (#10344) 2025-09-11 11:19:01 +00:00
.gitignore feat: further release automation (#9092) 2025-06-30 05:44:10 +00:00
.gitpod.Dockerfile chore: add gitpod configuration (#6382) 2024-12-15 21:38:13 +00:00
.gitpod.yml chore: add gitpod configuration (#6382) 2024-12-15 21:38:13 +00:00
.ignore chore: ignore stage0/ (for rg etc.) 2022-03-18 15:28:20 +01:00
CMakeLists.txt chore: make USE_LAKE the default (#10016) 2025-08-21 11:43:25 +00:00
CMakePresets.json chore: fix reldebug preset (#8051) 2025-04-23 10:05:11 +00:00
CODEOWNERS chore: make datokrat code owner for iterators, ranges and slices (#9667) 2025-08-01 17:34:43 +00:00
CONTRIBUTING.md doc: triage 2024-07-26 18:24:06 +02:00
flake.lock chore: robustify Nix shell (#8141) 2025-04-28 15:08:32 +00:00
flake.nix chore: remove broken Nix build (#9910) 2025-08-14 08:31:39 +00:00
lean-toolchain doc: VS Code dev setup (#2961) 2023-11-30 08:35:03 +00:00
lean.code-workspace feat: overhaul meta system (#10362) 2025-09-17 21:04:29 +00:00
LICENSE chore: remove LICENSE header that confused GitHub 2021-11-18 09:42:35 +01:00
LICENSES feat: ship cadical (#4325) 2024-08-23 09:13:27 +00:00
README.md doc: update URLs that are currently pointing to redirects (#10397) 2025-09-17 15:50:07 +00:00
RELEASES.md chore: updates to release_checklist.md (#7817) 2025-04-04 03:45:36 +00:00

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.