lean4-htt/tests/elab/letrecInProofs.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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2.6 KiB
Text

import Lean
inductive Tree
| leaf : Tree
| node : Tree → Tree → Tree
abbrev notSubtree (x : Tree) (t : Tree) : Prop :=
t.rec True fun l r l_ih r_ih => (x ≠ l ∧ l_ih) ∧ (x ≠ r ∧ r_ih)
infix:50 "≮" => notSubtree
theorem Tree.acyclic (x t : Tree) : x = t → x ≮ t := by
let rec right (x s : Tree) (b : Tree) (h : x ≮ b) : node s x ≠ b ∧ node s x ≮ b := by
match b, h with
| leaf, h =>
apply And.intro _ trivial
intro h; injection h
| node l r, h =>
have ihl : x ≮ l → node s x ≠ l ∧ node s x ≮ l := right x s l
have ihr : x ≮ r → node s x ≠ r ∧ node s x ≮ r := right x s r
have hl : x ≠ l ∧ x ≮ l := h.1
have hr : x ≠ r ∧ x ≮ r := h.2
have ihl : node s x ≠ l ∧ node s x ≮ l := ihl hl.2
have ihr : node s x ≠ r ∧ node s x ≮ r := ihr hr.2
apply And.intro
focus
intro h
injection h with _ h
exact absurd h hr.1
done
focus
apply And.intro
apply ihl
apply ihr
let rec left (x t : Tree) (b : Tree) (h : x ≮ b) : node x t ≠ b ∧ node x t ≮ b := by
match b, h with
| leaf, h =>
apply And.intro _ trivial
intro h; injection h
| node l r, h =>
have ihl : x ≮ l → node x t ≠ l ∧ node x t ≮ l := left x t l
have ihr : x ≮ r → node x t ≠ r ∧ node x t ≮ r := left x t r
have hl : x ≠ l ∧ x ≮ l := h.1
have hr : x ≠ r ∧ x ≮ r := h.2
have ihl : node x t ≠ l ∧ node x t ≮ l := ihl hl.2
have ihr : node x t ≠ r ∧ node x t ≮ r := ihr hr.2
apply And.intro
focus
intro h
injection h with h _
exact absurd h hl.1
done
focus
apply And.intro
apply ihl
apply ihr
let rec aux : (x : Tree) → x ≮ x
| leaf => trivial
| node l r => by
have ih₁ : l ≮ l := aux l
have ih₂ : r ≮ r := aux r
show (node l r ≠ l ∧ node l r ≮ l) ∧ (node l r ≠ r ∧ node l r ≮ r)
apply And.intro
focus
apply left
assumption
focus
apply right
assumption
intro h
subst h
apply aux
open Tree
theorem ex1 (x : Tree) : x ≠ node leaf (node x leaf) := by
intro h
exact absurd rfl $ Tree.acyclic _ _ h |>.2.2.1.1
theorem ex2 (x : Tree) : x ≠ node x leaf := by
intro h
exact absurd rfl $ Tree.acyclic _ _ h |>.1.1
theorem ex3 (x y : Tree) : x ≠ node y x := by
intro h
exact absurd rfl $ Tree.acyclic _ _ h |>.2.1