This returns a simple string of length size, each of whose characters has been initialized to the :initial-element argument. If an :initial-element argument is not specified, then the string will be initialized in an implementation-dependent way.

The :element-type argument names the type of the elements of the string; a string is constructed of the most specialized type that can accommodate elements of the given type. If :element-type is omitted, the type character is the default.

X3J13 voted in January 1989 to clarify that the size argument must be a non-negative integer less than the value of array-dimension-limit.

string-trim returns a substring of string, with all characters in character-bag stripped off the beginning and end. The function string-left-trim is similar but strips characters off only the beginning; string-right-trim strips off only the end. The argument character-bag may be any sequence containing characters. For example:

If no characters need to be trimmed from the string, then either the argument string itself or a copy of it may be returned, at the discretion of the implementation.

string-upcase returns a string just like string with all lowercase characters replaced by the corresponding uppercase characters. More precisely, each character of the result string is produced by applying the function char-upcase to the corresponding character of string.

string-downcase is similar, except that uppercase characters are converted to lowercase characters (using char-downcase).

The keyword arguments :start and :end delimit the portion of the string to be affected. The result is always of the same length as string, however.

The argument is not destroyed. However, if no characters in the argument require conversion, the result may be either the argument or a copy of it, at the implementation’s discretion. For example:

string-capitalize produces a copy of string such that, for every word in the copy, the first character of the word, if case-modifiable, is uppercase and any other case-modifiable characters in the word are lowercase. For the purposes of string-capitalize, a word is defined to be a consecutive subsequence consisting of alphanumeric characters or digits, delimited at each end either by a non-alphanumeric character or by an end of the string. For example:

These three functions are just like string-upcase, string-downcase, and string-capitalize but destructively modify the argument string by altering case-modifiable characters as necessary.

The keyword arguments :start and :end delimit the portion of the string to be affected. The argument string is returned as the result.

Most of the string functions effectively apply string to such of their arguments as are supposed to be strings. If x is a string, it is returned. If x is a symbol, its print name is returned.

In any other situation, an error is signaled.

To convert a sequence of characters to a string, use coerce. (Note that (coerce x ’string) will not succeed if x is a symbol. Conversely, string will not convert a list or other sequence to be a string.)

To get the string representation of a number or any other Lisp object, use prin1-to-string, princ-to-string, or format.