lean4-htt/tests/lean/run/grind_countP.lean
Leonardo de Moura c28b052576
feat: [grind?] attribute (#8426)
This PR adds the attribute `[grind?]`. It is like `[grind]` but displays
inferred E-matching patterns. It is a more convinient than writing.
Thanks @kim-em for suggesting this feature.
```lean
set_option trace.grind.ematch.pattern true
```
This PR also improves some tests, and adds helper function
`ENode.isRoot`.
2025-05-21 00:32:49 +00:00

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set_option grind.warning false
variable {α : Type u} {l : List α} {P Q : α → Bool}
attribute [grind] List.countP_nil List.countP_cons
theorem List.countP_le_countP (hpq : ∀ x ∈ l, P x → Q x) :
l.countP P ≤ l.countP Q := by
induction l <;> grind
-- TODO: how to explain to the user that `l.countP P ≤ l.countP Q` is a bad pattern
grind_pattern List.countP_le_countP => l.countP P, l.countP Q
theorem List.countP_lt_countP (hpq : ∀ x ∈ l, P x → Q x) (y:α) (hx: y ∈ l) (hxP : P y = false) (hxQ : Q y) :
l.countP P < l.countP Q := by
induction l <;> grind
/--
info: List.countP_nil: [@List.countP #1 #0 (@List.nil _)]
---
info: List.countP_cons: [@List.countP #3 #2 (@List.cons _ #1 #0)]
-/
#guard_msgs (info) in
attribute [grind?] List.countP_nil List.countP_cons