Joe Hendrix
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ac7b95da86
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feat: port Batteries.WF for executable well-founded fixpoints (#11620)
This PR ports Batteries.WF to Init.WFC for executable well-founded
fixpoints. It introduces `csimp` theorems to replace the recursors and
non-executable definitions with executable definitions.
This ocassionally comes up on Zulip as it prevents admiting definitions
generated from well-founded induction. (e.g., [#lean4 > Computable
WellFounded.fix](https://leanprover.zulipchat.com/#narrow/channel/270676-lean4/topic/Computable.20WellFounded.2Efix/with/529347861)
and [#mathlib4 > Why Nat.find is computable, when Wellfounded.fix
isn't?](https://leanprover.zulipchat.com/#narrow/channel/287929-mathlib4/topic/Why.20Nat.2Efind.20is.20computable.2C.20when.20Wellfounded.2Efix.20isn't.3F/with/545143617)).
This was motivated by running into poor elaboration performance with
recursive definitions involving complex inductive types generated by a
custom elaborator. It would be helpful to explore bypassing the
elaborator and generating elaborated terms directly, but this requires
an executable fixpoint (such as `WellFounded.fixC` introduced in
batteries).
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2025-12-12 18:22:54 +00:00 |
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