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19 lines
465 B
Idris
19 lines
465 B
Idris
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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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data Elem : a -> Vect n a -> Type where
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Here : Elem x (x :: xs)
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There : {xs : Vect n a} -> Elem x xs -> Elem x (y :: xs)
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getIndex : Elem x xs -> Nat
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getIndex Here = 0
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getIndex (There p) = S (getIndex p)
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Beatles : Vect ? String
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Beatles = ["John", "Paul", "George", "Ringo"]
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georgeInBeatles : Elem "George" Beatles
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georgeInBeatles = There (There Here)
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