mirror of
https://github.com/idris-lang/Idris2.git
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139 lines
3.0 KiB
Idris
139 lines
3.0 KiB
Idris
module Data.List1
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%default total
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infixr 7 :::
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public export
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record List1 a where
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constructor (:::)
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head : a
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tail : List a
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------------------------------------------------------------------------
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-- Conversion
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||| Forget that a list is non-empty
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public export
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forget : (1 xs : List1 a) -> List a
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forget (x ::: xs) = x :: xs
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||| Check whether a list is non-empty
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export
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fromList : (1 xs : List a) -> Maybe (List1 a)
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fromList [] = Nothing
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fromList (x :: xs) = Just (x ::: xs)
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------------------------------------------------------------------------
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-- Basic functions
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public export
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singleton : (1 x : a) -> List1 a
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singleton a = a ::: []
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export
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last : List1 a -> a
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last (x ::: xs) = loop x xs where
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loop : a -> List a -> a
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loop x [] = x
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loop _ (x :: xs) = loop x xs
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export
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foldr1' : (a -> b -> b) -> (a -> b) -> List1 a -> b
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foldr1' c n (x ::: xs) = loop x xs where
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loop : a -> List a -> b
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loop a [] = n a
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loop a (x :: xs) = c a (loop x xs)
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export
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foldr1 : (a -> a -> a) -> List1 a -> a
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foldr1 c = foldr1' c id
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export
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foldl1 : (a -> b) -> (b -> a -> b) -> List1 a -> b
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foldl1 n c (x ::: xs) = foldl c (n x) xs
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------------------------------------------------------------------------
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-- Append
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export
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appendl : (1 xs : List1 a) -> (1 ys : List a) -> List1 a
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appendl (x ::: xs) ys = x ::: xs ++ ys
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export
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append : (1 xs, ys : List1 a) -> List1 a
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append xs ys = appendl xs (forget ys)
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export
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lappend : (1 xs : List a) -> (1 ys : List1 a) -> List1 a
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lappend [] ys = ys
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lappend (x :: xs) ys = append (x ::: xs) ys
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------------------------------------------------------------------------
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-- Cons/Snoc
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public export
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cons : (1 x : a) -> (1 xs : List1 a) -> List1 a
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cons x xs = x ::: forget xs
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export
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snoc : (1 xs : List1 a) -> (1 x : a) -> List1 a
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snoc xs x = append xs (singleton x)
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------------------------------------------------------------------------
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-- Reverse
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public export
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reverseOnto : (1 acc : List1 a) -> (1 xs : List a) -> List1 a
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reverseOnto acc [] = acc
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reverseOnto acc (x :: xs) = reverseOnto (x ::: forget acc) xs
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public export
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reverse : (1 xs : List1 a) -> List1 a
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reverse (x ::: xs) = reverseOnto (singleton x) xs
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------------------------------------------------------------------------
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-- Instances
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export
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Semigroup (List1 a) where
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(<+>) = append
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export
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Functor List1 where
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map f (x ::: xs) = f x ::: map f xs
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export
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Applicative List1 where
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pure x = singleton x
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f ::: fs <*> xs = appendl (map f xs) (fs <*> forget xs)
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export
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Monad List1 where
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(x ::: xs) >>= f = appendl (f x) (xs >>= forget . f)
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export
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Foldable List1 where
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foldr c n (x ::: xs) = c x (foldr c n xs)
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export
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Show a => Show (List1 a) where
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show = show . forget
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export
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Eq a => Eq (List1 a) where
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(x ::: xs) == (y ::: ys) = x == y && xs == ys
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export
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Ord a => Ord (List1 a) where
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compare xs ys = compare (forget xs) (forget ys)
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------------------------------------------------------------------------
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-- Properties
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export
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consInjective : the (List1 a) (x ::: xs) === (y ::: ys) -> (x === y, xs === ys)
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consInjective Refl = (Refl, Refl)
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