e148871087
(Almost) only typos in constant names and doc-strings were considered; grammar was not considered. Also, along others, `mkDefinitionValInferrringUnsafe` has been fixed :-)
46 lines
1.7 KiB
Text
46 lines
1.7 KiB
Text
/-
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Copyright (c) 2025 Lean FRO, LLC. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Authors: Joachim Breitner
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-/
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module
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prelude
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public import Init.Prelude
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public import Init.Tactics
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public section
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set_option linter.unusedVariables false in
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/--
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The expression `binderNameHint v binder e` defined to be `e`.
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If it is used on the right-hand side of an equation that is used for rewriting by `rw` or `simp`,
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and `v` is a local variable, and `binder` is an expression that (after beta-reduction) is a binder
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(`fun w => …` or `∀ w, …`), then it will rename `v` to the name used in that binder, and remove
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the `binderNameHint`.
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A typical use of this gadget would be as follows; the gadget ensures that after rewriting, the local
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variable is still `name`, and not `x`:
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```
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theorem all_eq_not_any_not (l : List α) (p : α → Bool) :
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l.all p = !l.any fun x => binderNameHint x p (!p x) := sorry
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example (names : List String) : names.all (fun name => "Waldo".isPrefixOf name) = true := by
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rw [all_eq_not_any_not]
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-- ⊢ (!names.any fun name => !"Waldo".isPrefixOf name) = true
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```
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If `binder` is not a binder, then the name of `v` attains a macro scope. This only matters when the
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resulting term is used in a non-hygienic way, e.g. in termination proofs for well-founded recursion.
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This gadget is supported by
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* `simp`, `dsimp` and `rw` in the right-hand-side of an equation
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* `simp` in the assumptions of congruence rules
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It is ineffective in other positions (hypotheses of rewrite rules) or when used by other tactics
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(e.g. `apply`).
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-/
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@[simp ↓, expose]
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def binderNameHint {α : Sort u} {β : Sort v} {γ : Sort w} (v : α) (binder : β) (e : γ) : γ := e
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