gistfile1.hs

module Hoge (
    fuga
) where

filter' :: (a -> Bool) -> [a] -> [a]
filter' _ [] = []
filter' p (x:xs) = (if p x then (x:) else id) $ filter' p xs

chain :: (Integral a) => a -> [a]
chain 1 = [1]
chain x = x : chain (if even x then x `div` 2 else 3*x+1)

fuga = hoge [(2,2)] --runtime error!
    where hoge xs = map (\(1,b) -> 1 + b) xs

map' :: (a -> b) -> [a] -> [b]
map' f xs = foldr (\x acc -> f x : acc) [] xs

map'' :: (a -> b) -> [a] -> [b]
map'' f xs = foldl (\acc x -> acc ++ [f x]) [] xs

foldl' :: (a -> b -> a) -> a -> [b] -> a
foldl' f acc [] = acc
foldl' f acc (x:xs) = foldl' f (f acc x) xs

foldr' :: (a -> b -> b) -> b -> [a] -> b
foldr' f acc [] = acc
foldr' f acc (x:xs) = f x $ foldr' f acc xs