41d310ab39
Rather than adding symm hypotheses to the local context, it now adds them to the list of hypotheses derived from the local context. This is not ideal for performance reasons, but it at least closes #3922. In the future, solveByElim could maintain its own cache of facts that it updates whenever it does intro.
37 lines
980 B
Text
37 lines
980 B
Text
/-!
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# Issue 3922
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The `apply?` tactic would apply `symm` to every hypothesis in the local context,
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leading to these new hypotheses being included in the term even if they weren't used.
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They also created unelaboratable terms such as `?_ (id (r.symm h₂))`.
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-/
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set_option linter.unusedVariables false
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-- set up a binary relation
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axiom r : Nat → Nat → Prop
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-- that is symmetric
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axiom r.symm {a b : Nat} : r a b → r b a
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-- and has some other property
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axiom r.trans {a b c : Nat} : r a b → r b c → r a c
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/--
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info: Try this: refine r.symm ?a✝
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---
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info: Try this: refine r.trans ?a✝ ?a✝¹
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---
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warning: declaration uses 'sorry'
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-/
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#guard_msgs (ordering := sorted) in
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example (a b c : Nat) (h₁ : r b a) (h₂ : r b c) : r c a := by
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apply?
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-- now attach the `symm` attribute to `r.symm`
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attribute [symm] r.symm
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/-- info: Try this: exact r.trans (id (r.symm h₂)) h₁ -/
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#guard_msgs in
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example (a b c : Nat) (h₁ : r b a) (h₂ : r b c) : r c a := by
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apply?
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