5cef84709f
See Section "Other goodies" at https://github.com/leanprover/lean/wiki/Refactoring-structures This commit also improves the support for projections in the unifier/matcher. Now, we consider the extra case-split for projections. Given a projection `proj`, and the constraint `proj s =?= proj t`, we need to try first `s =?= t` and if it fails, then try to reduce. This is needed in the standard library because we now have constraints such as: ``` @has_le.le ?A ?s ?a ?b =?= @has_le.le nat nat.has_add x y ``` If we reduce the right hand side, we get the unsolvable constraint ``` @has_le.le ?A ?s ?a ?b =?= nat.le x y ``` Before this change, the constraint was `@le ?A ?s ?a ?b =?= @le nat nat.has_add x y`, and we already perform a case-split in this case. Moreover, projections were eagerly reduced whenever possible. The extra case-split generates a performance problem in several tests. For example `fib 8 = 34` was timing out. I worked around this issue by performing the case-split only when the constraint contains meta-variables. There are also minor issues. Example. `<` is notation for `has_lt.lt`, but `>` is for `gt`.
12 lines
391 B
Text
12 lines
391 B
Text
example (a b : nat) (p : nat → nat → Prop) (h₁ : p a b) (h₂ : a = b) : p b b :=
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@@eq.subst (λ x, p x b) h₂ h₁
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set_option pp.all true
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variable my_has_add : has_add nat
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#check @@has_add.add my_has_add 0 1
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local notation h1 `▸[` m `]` h2 := @@eq.subst m h1 h2
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example (a b : nat) (p : nat → nat → Prop) (h₁ : p a b) (h₂ : a = b) : p b b :=
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h₂ ▸[λ x, p x b] h₁
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