string-upcase

(string-upcase string-designator &key (start 0) end)

Returns a new string with every lowercase letter converted to uppercase; the original string is unchanged. The argument is a string designator, so a symbol, a keyword or a character is also accepted -- a symbol's name is used and a keyword's leading colon is dropped, so (string-upcase :foo) returns "FOO" and (string-upcase #\a) returns "A". Anything that is not one of those three types is an error. Case conversion is full-Unicode and identical on every backend: each character is folded with char-upcase, so (string-upcase "éλω") returns "ÉΛΩ". Because the fold is per character, the result always has the same length as the argument -- there is no multi-character special casing ((string-upcase "straße") returns "STRAßE", not "STRASSE").

:start / :end bound the part that is converted; the characters outside it are kept as they are, and a nil :end means the end of the string. A range outside the string (:start below 0, :end past the length, or :start after :end) or a bound that is not an integer -- a nil :start included -- is the same type-error as subseq's, on every backend.