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80 lines
1.4 KiB
Plaintext
80 lines
1.4 KiB
Plaintext
use Optional None Some
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lenLit : [a] -> Nat
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lenLit l = case l of
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[] -> 0
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[_] -> 1
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[_, _] -> 2
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[_, _, _] -> 3
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lenCons : [a] -> Nat
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lenCons l = case l of
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[] -> 0
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_ +: t -> 1 + lenCons t
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_ +: (_ +: t) -> 2 + lenCons t
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lenSnoc : [a] -> Nat
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lenSnoc l = case l of
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[] -> 0
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t :+ _ -> 1 + lenSnoc t
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lenConcat1 : [a] -> Nat
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lenConcat1 l = case l of
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[] -> 0
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[_] ++ tail -> 1 + lenConcat1 tail
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lenConcat2 : [a] -> Nat
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lenConcat2 l = case l of
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[] -> 0
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prefix ++ [_] -> 1 + lenConcat2 prefix
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> lenLit [1, 2, 3]
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> lenCons [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
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> lenSnoc [1, 2, 3, 4, 5, 6, 7, 8]
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> lenConcat1 [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
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> lenConcat2 [1, 2, 3, 4, 5]
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head : [a] -> Optional a
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head l = case l of
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h +: _ -> Some h
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_ -> None
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> head []
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> head [1, 2, 3]
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firstTwo : [a] -> Optional (a, a)
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firstTwo l = case l of
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x +: (y +: _) -> Some (x, y)
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_ -> None
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> firstTwo []
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> firstTwo [1]
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> firstTwo [1, 2, 3]
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lastTwo : [a] -> Optional (a, a)
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lastTwo l = case l of
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_ :+ x :+ y -> Some (x, y)
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_ -> None
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> lastTwo []
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> lastTwo [1]
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> lastTwo [1, 2, 3]
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middle : [a] -> Optional [a]
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middle l = case l of
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[_] ++ m ++ [_] -> Some m
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_ -> None
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> middle []
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> middle [1, 2]
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> middle [1, 2, 3, 4, 5, 6]
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middleNel: [a] -> Optional (a, [a])
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middleNel l = case l of
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[_] ++ (h +: t) ++ [_] -> Some (h, t)
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_ -> None
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> middleNel []
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> middleNel [1, 2]
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> middleNel [1, 2, 3, 4, 5, 6]
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