Real World Haskell - 第4章 Part1 like a "laundry list"

Chapter 4. Functional programming
Chapter 4. Functional programming

Infix functions

infix notations is purely a syntactic convenience

Woking with lists

:module +Data.List
length :: [a] -> Int
- 全要素を参照するので不用意に使うと無限ループになる
null :: [a] -> Bool
head :: [a] -> a
tail :: [a] -> [a]
last :: [a] -> a
init :: [a] -> [a]

Partial and total functions

Functions that only have return values defined for a subset of valid inputs are called partial functions (calling error doesn't qualify as returning a value!). We call functions that return valid results over their entire input domains total functions.

head などは partial だけど unsafe と付いていない

More simple list manipulations

(++) :: [a] -> [a] -> [a]
- append
concat :: a -> [a]
reverse :: [a] -> [a]
and :: [Bool] -> Bool
or :: [Bool] -> Bool
all :: (a -> Bool) -> [a] -> Bool
any :: (a -> Bool) -> [a] -> Bool

Wroking with sublists

take :: Int -> [a] -> [a]
drop :: Int -> [a] -> [a]
splitAt :: Int -> [a] -> ([a], [a])
takeWhile :: (a -> Bool) -> [a] -> [a]
dropWhile :: (a -> Bool) -> [a] -> [a]
span :: (a -> Bool) -> [a] -> ([a], [a])
break :: (a -> Bool) -> [a] -> ([a], [a])

Searching lists

elem :: (Eq a) => a -> [a] -> Bool
filter :: (a -> Bool) -> [a] -> [a]
:module +Data.List
- isPrefixOf :: (Eq a) => [a] -> [a] -> Bool
- isInfixOf :: (Eq a) => [a] -> [a] -> Bool
- isSuffixOf :: (Eq a) => [a] -> [a] -> Bool

Working with several lists at once

zip :: [a] -> [b] -> [(a, b)]
- zip7 まである
zipWith :: (a -> b -> c) -> [a] -> [b] -> [c]
- zipWith7 まである

Prelude> :module +Data.List
Prelude Data.List> :type zip7
zip7 :: [a]
        -> [b]
        -> [c]
        -> [d]
        -> [e]
        -> [f]
        -> [g]
        -> [(a, b, c, d, e, f, g)]
Prelude Data.List> :type zipWith7
zipWith7 :: (a -> b -> c -> d -> e -> f -> g -> h)
            -> [a]
            -> [b]
            -> [c]
            -> [d]
            -> [e]
            -> [f]
            -> [g]
            -> [h]
Prelude Data.List>

Special string-handling functions

lines :: String -> [String]
unlines :: [String] -> String
words :: String -> [String]
unwords :: [String] -> String