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.
13 lines
423 B
Text
13 lines
423 B
Text
def Nat.hasDecEq: (a: Nat) → (b: Nat) → Decidable (Eq a b)
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| 0, 0 => isTrue rfl
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| n+1, 0
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| 0, n+1 => isFalse Nat.noConfusion
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| n+1, m+1 =>
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match h:hasDecEq n m with -- it works without `h:`
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| isTrue heq => isTrue (heq ▸ rfl)
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| isFalse hne => isFalse (Nat.noConfusion · (λ heq => absurd heq hne))
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termination_by a b => (a, b)
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set_option pp.proofs true
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#print Nat.hasDecEq
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#print Nat.hasDecEq._unary
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