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

See Data.List for operations on lists.

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

Methods

fromString :: String -> a Source #

Instances

Splits the argument into a list of lines stripped of their terminating \n characters. The \n terminator is optional in a final non-empty line of the argument string.

For example:

>>> lines "" -- empty input contains no lines
[]
>>> lines "\n" -- single empty line
[""]
>>> lines "one" -- single unterminated line
["one"]
>>> lines "one\n" -- single non-empty line
["one"]
>>> lines "one\n\n" -- second line is empty
["one",""]
>>> lines "one\ntwo" -- second line is unterminated
["one","two"]
>>> lines "one\ntwo\n" -- two non-empty lines
["one","two"]

When the argument string is empty, or ends in a \n character, it can be recovered by passing the result of lines to the unlines function. Otherwise, unlines appends the missing terminating \n. This makes unlines . lines idempotent:

(unlines . lines) . (unlines . lines) = (unlines . lines)

words breaks a string up into a list of words, which were delimited by white space (as defined by isSpace ). This function trims any white spaces at the beginning and at the end.

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

Appends a \n character to each input string, then concatenates the results. Equivalent to foldMap (s -> s ++ "\n").

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

Note that unlines . lines /= id when the input is not \n-terminated:

>>> unlines . lines $ "foo\nbar"
"foo\nbar\n"

unwords joins words with separating spaces (U+0020 SPACE).

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

unwords is neither left nor right inverse of words :

>>> words (unwords [" "])
[]
>>> unwords (words "foo\nbar")
"foo bar"