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Pair が関手（functor）であることを示す例 #1154

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Seasawher opened this issue Nov 23, 2024 · 0 comments

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コード例型クラス

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Seasawher commented Nov 23, 2024

/-- 与えられた型の対を作る -/
def Pair (α : Type) : Type := α × α

/-- `Pair` を関手にする -/
instance : Functor Pair where
  map f := fun a => (f a.fst, f a.snd)

macro "functor" : tactic => `(tactic| constructor <;> aesop)

instance : LawfulFunctor Pair := by 
  functor

Seasawher added コード例型クラス labels

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