Squeaky Clean

Strings

Characters and Strings form the basis for text representation in Elm. Strings can be thought of as lists of characters and most List functions have their equivalent in the String module.

Characters

The Char type represents a single unicode character with single quotes e.g. 'a'. The Char module provides predicate functions (Char -> Bool) to test qualities of a character: isUpper, isLower, isAlpha, and isAlphaNum The module also provides functions to convert a character toUpper, toLower, toLocaleUpper, toLocaleLower, as well as to/from their numerical unicode value (Int) with toCode and fromCode.

Strings

The String type provides a built-in representation for efficient string manipulation and can represent any sequence of unicode characters e.g. "this is an Elm string." Multi-line strings are represented with triple double quotes and can have unescaped quotes and newlines.

"""
    This is a multiline string.
All line-breaks and whitespace,
are preserved. 
"""

String Functions

The String module contains all the functions summarized on the table below. Some of the most commonly used functions include:

cons : Char -> String -> String adds a character to the beginning of a string.

cons 'T' "he truth is out there" 
    --> "The truth is out there"

(++): String -> String -> String appends two strings.

"butter" ++ "fly" 
    --> "butterfly"

split : String -> String -> List String splits a string into a list of strings at the given separator.

split ";" "cat;dog;cow" 
    --> ["cat", "dog", "cow"]

join : String -> List String -> String concatenates a list of strings together with a given separator.

join "a" ["H", "w", "ii", "n"] 
    --> "Hawaiian"

replace : String -> String -> String -> String replaces all occurrences of a given substring.

replace "Hello" "Goodbye cruel" "Hello world." 
    --> "Goodbye cruel world."

length : String -> Int returns the number of characters in a string.

length "Hello world." 
    --> 12

toInt : String -> Maybe Int tries to convert a string into Just Int, and returns Nothing for improperly formatted strings.

toInt "-42" 
    --> Just -42

contains : String -> String -> Bool checks if the second string contains the first one.

contains "the" "theory" 
    --> True

map : (Char -> Char) -> String -> String applies a given function to every Char in the string. Note the function provided must be a mapping from and to Char.

map (\c -> if c == '/' then '.' else c) "a/b/c" 
    --> "a.b.c"

All String Functions: