b5122b6a7b
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.
43 lines
823 B
Text
43 lines
823 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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all_goals simp_wf
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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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all_goals simp_wf
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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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