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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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Joachim Breitner 5cd90f5826
feat: drop support for termination_by' (#3033) 
until around 7fe6881 the way to define well-founded recursions was to
specify a `WellFoundedRelation` on the argument explicitly. This was
rather low-level, for example one had to predict the packing of multiple
arguments into `PProd`s, the packing of mutual functions into `PSum`s,
and the cliques that were calculated.

Then the current `termination_by` syntax was introduced, where you
specify the termination argument at a higher level (one clause per
functions, unpacked arguments), and the `WellFoundedRelation` is found
using type class resolution.

The old syntax was kept around as `termination_by'`. This is not used
anywhere in the lean, std, mathlib or the theorem-proving-in-lean
repositories,
and three occurrences I found in the wild can do without

In particular, it should be possible to express anything that the old
syntax
supported also with the new one, possibly requiring a helper type with a
suitable instance, or the following generic wrapper that now lives in
std
```
def wrap {α : Sort u} {r : α → α → Prop} (h : WellFounded r) (x : α) : {x : α // Acc r x}
```

Since the old syntax is unused, has an unhelpful name and relies on
internals, this removes the support. Now is a good time before the
refactoring that's planned in #2921.

The test suite was updated without particular surprises.

The parametric `terminationHint` parser is gone, which means we can
match on syntax more easily now, in `expandDecreasingBy?`.
2023-12-11 17:33:17 +00:00
.github chore: stage0 autoupdater action (#3042) 2023-12-11 09:50:27 +00:00
doc chore: stage0 autoupdater action (#3042) 2023-12-11 09:50:27 +00:00
images
nix chore: set warningAsError in CI only (#3030) 2023-12-06 08:18:39 +00:00
script chore: script/most-recent-nightly-tag uses https rather than ssh repo URL (#2951) 2023-11-23 10:27:46 +00:00
src feat: drop support for termination_by' (#3033) 2023-12-11 17:33:17 +00:00
stage0 feat: drop support for termination_by' (#3033) 2023-12-11 17:33:17 +00:00
tests feat: drop support for termination_by' (#3033) 2023-12-11 17:33:17 +00:00
.gitattributes chore: Do not hide stage0/src/stdlib_flags.h from diffs 2023-09-13 19:29:25 +02:00
.gitignore chore: update tests to account for .lake 2023-11-13 20:31:24 -05:00
.ignore chore: ignore stage0/ (for rg etc.) 2022-03-18 15:28:20 +01:00
CMakeLists.txt feat: embed and check githash in .olean (#2766) 2023-11-27 10:24:43 +00:00
CODEOWNERS doc: widget code owner 2023-12-01 15:46:45 +00:00
CONTRIBUTING.md doc: Adjust contributor's docs to squash merging (#2927) 2023-11-21 10:13:43 +00:00
default.nix doc: setup 2021-01-03 13:21:58 +01:00
flake.lock chore: Nix bump to LLVM 15 2023-07-28 10:56:54 +02:00
flake.nix chore: Nix: use strings instead of URL literals (#2172) 2023-03-28 10:10:24 +02:00
lean-toolchain doc: VS Code dev setup (#2961) 2023-11-30 08:35:03 +00:00
lean.code-workspace chore: add vscode cmake configuration (#3008) 2023-12-04 16:35:03 +00:00
LICENSE chore: remove LICENSE header that confused GitHub 2021-11-18 09:42:35 +01:00
LICENSES chore: add GMP license for now 2021-11-18 09:42:35 +01:00
README.md doc: Update contribution guides (#2624) 2023-10-25 13:05:55 +11:00
RELEASES.md feat: drop support for termination_by' (#3033) 2023-12-11 17:33:17 +00:00
shell.nix chore: Nix bump to LLVM 15 2023-07-28 10:56:54 +02:00

README.md

This is the repository for Lean 4.

We provide nightly releases and have just begun regular stable point releases.

About

Installation

See Setting Up Lean.

Contributing

Please read our Contribution Guidelines first.

Building from Source

See Building Lean.