lean-ja / lean-ja/lean-by-example
遅延評価を入れると矛盾が生じる例
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Description
lean-ja Discordより
-- Assume we can define `ones := 1 :: ones`.
opaque ones : List Nat
axiom ones_eq : ones = 1 :: ones
theorem bad : ones.foldr (· + ·) 0 = ones.foldr (· + ·) 0 + 1 := by
conv =>
lhs
rw [ones_eq, List.foldr_cons]
omega
-- 🤯
example : False := Nat.ne_add_one (ones.foldr (· + ·) 0) bad
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Research direction
The issue contains only a Lean example using ones_eq, List.foldr, and omega; no repository file or test is named. Start by reproducing the example and checking the relevant Lean semantics. Done should be a documented explanation of whether this demonstrates a language inconsistency or needs clarification.
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Assessment
- Domain
- compilers
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 20/100