49 lines
1.0 KiB
Haskell
49 lines
1.0 KiB
Haskell
{-| Basic padding and "justification" of lists. -}
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module Padding
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( leftPad
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, rightPad
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, midPad
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, midPadL
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, rotU
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, rotD
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, rotListAt
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)
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where
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leftPad :: Int -> a -> [a] -> [a]
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{-# INLINE leftPad #-}
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leftPad i x xs = reverse $ take i $ reverse (take i xs) ++ repeat x
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rightPad :: Int -> a -> [a] -> [a]
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{-# INLINE rightPad #-}
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rightPad i x xs = take i $ xs ++ repeat x
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midPad :: Int -> a -> [a] -> [a] -> [a]
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{-# INLINE midPad #-}
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midPad i x xs ys = xs ++ replicate j x ++ ys
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where
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j = i - (length xs + length ys)
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midPadL :: Int -> a -> [a] -> [a] -> [a]
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{-# INLINE midPadL #-}
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midPadL i x xs ys = take j (xs ++ repeat x) ++ ys
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where
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j = i - length ys
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rotU :: [a] -> [a]
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{-# INLINE rotU #-}
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rotU [] = []
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rotU (x:xs) = xs ++ [x]
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rotD :: [a] -> [a]
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{-# INLINE rotD #-}
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rotD [] = []
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rotD xs = last xs : init xs
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rotListAt :: Eq a => a -> [a] -> [a]
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rotListAt x' xs = f x' xs []
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where
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f x (y:ys) zs
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| y == x = y:ys ++ zs
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| otherwise = f x ys (y:zs)
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f _ [] zs = zs
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