65 lines
1.7 KiB
Haskell
65 lines
1.7 KiB
Haskell
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module Util where
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import ParseLib ( (<$>), (<*>), (<*), (*>), (<$), Parser, parse )
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import System.IO ( IOMode(ReadMode), openFile, hGetContents )
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-- Functions on lists
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count :: Eq a => [a] -> a -> Int
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count xs find = length (filter (== find) xs)
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-- Helper IO functions
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getFileContents :: FilePath -> IO String
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getFileContents filename = do
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handle <- openFile filename ReadMode
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hGetContents handle
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-- Helper functions for the utrecht parser combinator lib
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-- Rename operators
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(<$$>) :: (a -> b) -> Parser s a -> Parser s b
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(<$$>) = (ParseLib.<$>)
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(<$$) :: b -> Parser s a -> Parser s b
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(<$$) = (ParseLib.<$)
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(<$*>) :: Parser s (b -> a) -> Parser s b -> Parser s a
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(<$*>) = (ParseLib.<*>)
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(<$*) :: Parser s a -> Parser s b -> Parser s a
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(<$*) = (ParseLib.<*)
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($*>) :: Parser s a -> Parser s b -> Parser s b
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($*>) = (ParseLib.*>)
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tryparse :: Parser s a -> [s] -> a
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tryparse lexer input = case parse lexer input of
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(ls : _) -> fst ls
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_ -> error "Parsing failed"
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-- A monoid that calculates the difference between two numbers
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newtype Difference a = Difference {unwrap :: a} deriving (Show)
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instance (Num a) => Semigroup (Difference a) where
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(<>) (Difference a) (Difference b) = Difference (abs $ b - a)
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instance (Num a) => Monoid (Difference a) where
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mempty = Difference 0
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-- List's applicative fmap creates a "cartesian" product.
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-- This applies the functor pairwise (which is what you usually want?)
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newtype Pairwise a = Pairwise {getPairwise :: [a]} deriving (Show)
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instance Functor (Pairwise) where
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fmap f (Pairwise as) = Pairwise $ fmap f as
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instance Applicative (Pairwise) where
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pure x = Pairwise (pure x)
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(<*>) (Pairwise fs) (Pairwise xs) =
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Pairwise (zipWith ($) fs xs)
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