string-upcase, string-downcase, string-titlecase, string-foldcase - string case conversion

---

LIBRARY

(import (rnrs))                     ;R6RS
(import (rnrs unicode))             ;R6RS
(import (scheme char))              ;R7RS

SYNOPSIS

(string-upcase string)
(string-downcase string)
(string-titlecase string)           ;R6RS
(string-foldcase string)

DESCRIPTION

string-upcase

Converts a string to upper case.

string-downcase

Converts a string to lower case.

string-foldcase

Converts the string to its case-folded counterpart, using the full case-folding mapping, but without the special mappings for Turkic languages.

string-titlecase

Converts the first cased character of each word, and downcases all other cased characters.

These procedures are defined in terms of Unicode's locale-independent case mappings from Unicode scalar-value sequences to scalar-value sequences. In particular, the length of the result string can be different from the length of the input string.

Since these procedures are locale-independent, they may not be appropriate for some locales.

R7RS

The Unicode Standard prescribes special treatment of the Greek letter Σ, whose normal lower-case form is σ but which becomes ς at the end of a word. See Unicode Standard Annex #44 for details. However, implementations of string-downcase are not required to provide this behavior, and may choose to change Σ to σ in all cases.

IMPLEMENTATION NOTES

Word breaking, as needed for the correct casing of Σ and for string-titlecase, is specified in Unicode Standard Annex #29.

RETURN VALUES

When the specified result is equal in the sense of string=?(3scm) to the argument, these procedures may return the argument instead of a newly allocated string.

EXAMPLES

(string-upcase "Hi")               =>  "HI"
(string-downcase "Hi")             =>  "hi"
(string-foldcase "Hi")             =>  "hi"
(string-upcase "Straße")           =>  "STRASSE"
(string-downcase "Straße")         =>  "straße"
(string-foldcase "Straße")         =>  "strasse"
(string-downcase "STRASSE")        =>  "strasse"
(string-downcase "Σ")              =>  "σ"

;; Chi Alpha Omicron Sigma.
;; See the note on R7RS in the description.
(string-upcase "XAOΣ")             =>  "XAOΣ"
(string-downcase "XAOΣ")           =>  "χαoς"
(string-downcase "XAOΣΣ")          =>  "χαoσς"
(string-downcase "XAOΣ Σ")         =>  "χαoς σ"
(string-foldcase "XAOΣΣ")          =>  "χαoσσ"
(string-upcase "χαoς")             =>  "XAOΣ"
(string-upcase "χαoσ")             =>  "XAOΣ"

(string-titlecase "kNock KNoCK")   =>  "Knock Knock"
(string-titlecase "who's there?")  =>  "Who's There?"
(string-titlecase "r6rs")          =>  "R6rs"
(string-titlecase "R6RS")          =>  "R6rs"

COMPATIBILITY

ERRORS

&assertion (R6RS)

The wrong number of arguments was passed or an argument was outside its domain.

R7RS

The assertions described above are errors. Implementations may signal an error, extend the procedure's domain of definition to include such arguments, or fail catastrophically.

SEE ALSO

https://www.unicode.org/reports/tr44/Unicode Standard Annex #44: Unicode Character Database.

https://www.unicode.org/reports/tr29/Unicode Standard Annex #29: Unicode Text Segmentation.

STANDARDS

HISTORY

AUTHORS