lean4-htt/tests/lean/run/wfLean3Issue.lean
Joachim Breitner b5122b6a7b feat: per-function termination hints
This change

 * moves `termination_by` and `decreasing_by` next to the function they
   apply to
 * simplify the syntax of `termination_by`
 * apply the `decreasing_by` goal to all goals at once, for better
   interactive use.

See the section in `RELEASES.md` for more details and migration advise.

This is a hard breaking change, requiring developers to touch every
`termination_by` in their code base. We decided to still do it as a
hard-breaking change, because supporting both old and new syntax at the
same time would be non-trivial, and not save that much. Moreover, this
requires changes to some metaprograms that developers might have
written, and supporting both syntaxes at the same time would make
_their_ migration harder.
2024-01-10 17:27:35 +01:00

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def foo : Nat → Nat → Nat
| 0, 0 => 1
| s+1, 0 => foo s 0 + 1
| 0, b+1 => foo 0 b + 1
| s+1, b+1 => foo (s+1) b + foo s (b+1)
termination_by b s => (b, s)