This section describes functions for converting between characters,
strings and integers.
format (see Formatting Strings) and
prin1-to-string (see Output Functions) can also convert
Lisp objects into strings.
read-from-string (see Input Functions) can “convert” a string representation of a Lisp object
into an object. The functions
string-to-unibyte convert the text representation of a string
(see Converting Representations).
See Documentation, for functions that produce textual descriptions
of text characters and general input events
are used primarily for making help messages.
(number-to-string 256) ⇒ "256" (number-to-string -23) ⇒ "-23" (number-to-string -23.5) ⇒ "-23.5"
See also the function
formatin Formatting Strings.
This function returns the numeric value of the characters in string. If base is non-
nil, it must be an integer between 2 and 16 (inclusive), and integers are converted in that base. If base is
nil, then base ten is used. Floating-point conversion only works in base ten; we have not implemented other radices for floating-point numbers, because that would be much more work and does not seem useful. If string looks like an integer but its value is too large to fit into a Lisp integer,
string-to-numberreturns a floating-point result.
The parsing skips spaces and tabs at the beginning of string, then reads as much of string as it can interpret as a number in the given base. (On some systems it ignores other whitespace at the beginning, not just spaces and tabs.) If string cannot be interpreted as a number, this function returns 0.(string-to-number "256") ⇒ 256 (string-to-number "25 is a perfect square.") ⇒ 25 (string-to-number "X256") ⇒ 0 (string-to-number "-4.5") ⇒ -4.5 (string-to-number "1e5") ⇒ 100000.0
This function returns a new string containing one character, character. This function is semi-obsolete because the function
stringis more general. See Creating Strings.
This function returns the first character in string. This mostly identical to
(aref string 0), except that it returns 0 if the string is empty. (The value is also 0 when the first character of string is the null character, ASCII code 0.) This function may be eliminated in the future if it does not seem useful enough to retain.
Here are some other functions that can convert to or from a string: