View Source Unicode.String.Case.Folding (Unicode String v1.4.1)

Implements the Unicode Case Folding algorithm.

The intention of case folding is to facilitate case-insensitive string comparisons. It is not intended to be a general purpose transformation.

Although case folding does generally use lower case as its normal form, it is not true for all scripts and codepoints. Therefore case folding should not be used as an alternative to String.downcase/1.

Summary

Functions

fold(string)

Case fold a string.

fold(string, language)

Functions

fold(string)

Case fold a string.

Returns a string after applying the Unicode Case Folding algorithm.

Case folding is intended to suport case insensitve string comparisons such as that implemented by Unicode.String.equals_ignoring_case?/2 which calls this function on its parameters.

Arguments

string is any String.t()
mode or language tag is either the atoms :turkic or nil or a map that includes the key :language with a value that is a lowercase atom representing an ISO 639-1 language code. The CLDR language tag which is defined as part of the ex_cldr is one such example. See Cldr.validate_locale/2 for further information. The default is nil.

Returns

The case folded string

Notes

No normalization is applied to the string on either input or output.
Case folding does not apply any transformation to accented characters. "ü" will not case fold to "u" for example.

Examples

iex> Unicode.String.Case.Folding.fold("THIS")
"this"

iex> Unicode.String.Case.Folding.fold("grüßen")
"grüssen"

iex(13)> Unicode.String.Case.Folding.fold("I")
"i"

# Turkic languages such as Turkish and Azerbaijani have
# a dotless lower case "i"
iex> Unicode.String.Case.Folding.fold("I", :turkic)
"ı"

iex> Unicode.String.Case.Folding.fold("I", %{language: :az})
"ı"