lean4-htt/tests/elab/grind_palindromes.lean
Garmelon 08eb78a5b2
chore: switch to new test/bench suite (#12590)
This PR sets up the new integrated test/bench suite. It then migrates
all benchmarks and some related tests to the new suite. There's also
some documentation and some linting.

For now, a lot of the old tests are left alone so this PR doesn't become
even larger than it already is. Eventually, all tests should be migrated
to the new suite though so there isn't a confusing mix of two systems.
2026-02-25 13:51:53 +00:00

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module
@[expose] public section -- TODO: remove after we fix congr_eq
reset_grind_attrs%
attribute [grind cases] Or
inductive Palindrome : List α → Prop where
| nil : Palindrome []
| single : (a : α) → Palindrome [a]
| sandwich : (a : α) → Palindrome as → Palindrome ([a] ++ as ++ [a])
attribute [grind] Palindrome
attribute [grind =] List.cons_append List.nil_append List.reverse_cons List.reverse_append List.reverse_nil List.append_cancel_right_eq List.reverse_reverse
theorem palindrome_reverse (h : Palindrome as) : Palindrome as.reverse := by
induction h <;> grind
theorem reverse_eq_of_palindrome (h : Palindrome as) : as.reverse = as := by
induction h <;> grind
example (h : Palindrome as) : Palindrome as.reverse := by
grind [reverse_eq_of_palindrome]
def List.last : (as : List α) → as ≠ [] → α
| [a], _ => a
| _::a₂:: as, _ => (a₂::as).last (by grind)
@[grind] theorem List.last_cons (h₁ : as ≠ []) (h₂ : a :: as ≠ []): (a :: as).last h₂ = as.last h₁ := by
grind [last.eq_def]
@[grind] theorem List.dropLast_append_last (h : as ≠ []) : as.dropLast ++ [as.last h] = as := by
induction as, h using List.last.induct <;> grind [last, dropLast]
theorem List.palindrome_ind (motive : List α → Prop)
(h₁ : motive [])
(h₂ : (a : α) → motive [a])
(h₃ : (a b : α) → (as : List α) → motive as → motive ([a] ++ as ++ [b]))
(as : List α)
: motive as :=
match as with
| [] => h₁
| [a] => h₂ a
| a₁::a₂::as' =>
have ih := palindrome_ind motive h₁ h₂ h₃ (a₂::as').dropLast
have : [a₁] ++ (a₂::as').dropLast ++ [(a₂::as').last (by grind)] = a₁::a₂::as' := by grind
by grind
termination_by as.length
theorem List.palindrome_of_eq_reverse (h : as.reverse = as) : Palindrome as := by
induction as using palindrome_ind <;> grind
def List.isPalindrome [DecidableEq α] (as : List α) : Bool :=
as.reverse = as
theorem List.isPalindrome_correct [DecidableEq α] (as : List α) : as.isPalindrome ↔ Palindrome as := by
grind [isPalindrome, palindrome_of_eq_reverse, reverse_eq_of_palindrome]