d1174e10e6
Previously, the tactic state shown at `decreasing_by` would leak lots of details about the translation, and mention `invImage`, `PSigma` etc. This is not nice. So this introduces `clean_wf`, which is like `simp_wf` but using `simp`'s `only` mode, and runs this unconditionally. This should clean up the goal to a reasonable extent. Previously `simp_wf` was an unrestricted `simp […]` call, but we probably don’t want arbitrary simplification to happen at this point, so this now became `simp only` call. For backwards compatibility, `decreasing_with` begins with `try simp`. The `simp_wf` tactic is still available to not break too much existing code; it’s docstring suggests to no longer use it. With `set_option cleanDecreasingByGoal false` one can disable the use of `clean_wf`. I hope this is only needed for debugging and understanding. Migration advise: If your `decreasing_by` proof begins with `simp_wf`, either remove that (if the proof still goes through), or replace with `simp`. I am a bit anxious about running even `simp only` unconditionally here, as it may do more than some user might want, e.g. because of options like `zetaDelta := true`. We'll see if we need to reign in this tactic some more. I wonder if in corner cases the `simp_wf` tactic might be able to close the goal, and if that is a problem. If so, we may have to promote simp’s internal `mayCloseGoal` parameter to a simp configuration option and use that here. fixes #4928
41 lines
783 B
Text
41 lines
783 B
Text
namespace Ex1
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mutual
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def f : Nat → Bool → Nat
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| n, true => 2 * f n false
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| 0, false => 1
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| n, false => n + g n
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termination_by n b => (n, if b then 2 else 1)
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decreasing_by
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· apply Prod.Lex.right; decide
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· apply Prod.Lex.right; decide
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def g (n : Nat) : Nat :=
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if h : n ≠ 0 then
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f (n-1) true
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else
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n
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termination_by (n, 0)
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decreasing_by
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apply Prod.Lex.left
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apply Nat.pred_lt
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done -- should fail
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end
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end Ex1
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namespace Ex2
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mutual
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def f : Nat → Bool → Nat
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| n, true => 2 * f n false
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| 0, false => 1
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| n, false => n + g (n+1) -- Error
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termination_by n b => (n, if b then 2 else 1)
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def g (n : Nat) : Nat :=
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if h : n ≠ 0 then
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f (n-1) true
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else
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n
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termination_by (n, 0)
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end
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end Ex2
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