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https://github.com/idris-lang/Idris2.git
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41 lines
1.1 KiB
Idris
41 lines
1.1 KiB
Idris
data Vect : Nat -> Type -> Type where
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Nil : Vect Z a
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(::) : a -> Vect k a -> Vect (S k) a
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(++) : Vect n a -> Vect m a -> Vect (n + m) a
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(++) Nil ys = ys
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(++) (x :: xs) ys = x :: xs ++ ys
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data Fin : Nat -> Type where
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FZ : Fin (S k)
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FS : Fin k -> Fin (S k)
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index : Fin n -> Vect n a -> a
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index FZ (x :: xs) = x
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index (FS k) (x :: xs) = index k xs
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filter : (a -> Bool) -> Vect n a -> (p ** Vect p a)
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filter p Nil = (_ ** [])
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filter p (x :: xs)
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= case filter p xs of
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(_ ** xs') => if p x then (_ ** x :: xs')
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else (_ ** xs')
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cons : t -> (x : Nat ** Vect x t) -> (x : Nat ** Vect x t)
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cons val xs
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= record { fst = S (fst xs),
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snd = (val :: snd xs) } xs
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cons' : t -> (x : Nat ** Vect x t) -> (x : Nat ** Vect x t)
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cons' val
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= record { fst $= S,
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snd $= (val ::) }
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Show a => Show (Vect n a) where
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show xs = "[" ++ show' xs ++ "]" where
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show' : forall n . Vect n a -> String
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show' Nil = ""
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show' (x :: Nil) = show x
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show' (x :: xs) = show x ++ ", " ++ show' xs
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