nstring-upcase nstring-downcase nstring-capitalize

(nstring-upcase string) -- (nstring-downcase string) -- (nstring-capitalize string)

The destructive spellings of string-upcase, string-downcase and string-capitalize: the folded characters are written back into the argument, and the string is returned. The fold is the non-destructive sibling's, so the returned value is the same on every backend.

The write is real for a mutable character vector -- what make-string and (make-array n :element-type 'character) build: the very same object comes back, and a caller holding its own reference sees the change.

For an immutable string the compiled backends rebuild rather than write, which is the deviation every indexed write ((setf (aref s i) c), replace, fill) has there -- so the caller's own reference is left alone while the interpreter's is folded. Portable code uses the returned value, which is correct on all four backends.

The whole string is folded: like their non-destructive siblings these take no :start / :end. Each is a first-class function value, so #'nstring-upcase can be passed to funcall, mapcar or intern.

Backend support

All four backends -- one definition in rontolisp source, spliced into the program when it is referenced.