Data.String

The String type and associated operations.

Documentation

type String = [Char]

A String is a list of characters. String constants in Haskell are values of type String.

See Data.List for operations on lists.

class IsString a where

Class for string-like datastructures; used by the overloaded string extension (-XOverloadedStrings in GHC).

Methods

fromString :: String -> a

Instances

IsString a => IsString (Identity a)

Since: base-4.9.0.0

Defined in Data.String

Methods

fromString :: String -> Identity a

a ~ Char => IsString [a]

(a ~ Char) context was introduced in 4.9.0.0

Since: base-2.1

Defined in Data.String

Methods

fromString :: String -> [a]

IsString a => IsString (Const a b)

Since: base-4.9.0.0

Defined in Data.String

Methods

fromString :: String -> Const a b

Functions on strings

lines :: String -> [String]

lines breaks a string up into a list of strings at newline characters. The resulting strings do not contain newlines.

Note that after splitting the string at newline characters, the last part of the string is considered a line even if it doesn't end with a newline. For example,

>>> lines ""
[]

>>> lines "\n"
[""]

>>> lines "one"
["one"]

>>> lines "one\n"
["one"]

>>> lines "one\n\n"
["one",""]

>>> lines "one\ntwo"
["one","two"]

>>> lines "one\ntwo\n"
["one","two"]

Thus lines s contains at least as many elements as newlines in s.

words :: String -> [String]

words breaks a string up into a list of words, which were delimited by white space.

>>> words "Lorem ipsum\ndolor"
["Lorem","ipsum","dolor"]

unlines :: [String] -> String

unlines is an inverse operation to lines. It joins lines, after appending a terminating newline to each.

>>> unlines ["Hello", "World", "!"]
"Hello\nWorld\n!\n"

unwords :: [String] -> String

unwords is an inverse operation to words. It joins words with separating spaces.

>>> unwords ["Lorem", "ipsum", "dolor"]
"Lorem ipsum dolor"