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(elisp)String Conversion


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Conversion of Characters and Strings
====================================

   This section describes functions for conversions between characters,
strings and integers.  `format' and `prin1-to-string' (Note: Output
Functions) can also convert Lisp objects into strings.
`read-from-string' (Note: Input Functions) can "convert" a string
representation of a Lisp object into an object.  The functions
`string-make-multibyte' and `string-make-unibyte' convert the text
representation of a string (Note: Converting Representations).

   Note: Documentation, for functions that produce textual
descriptions of text characters and general input events
(`single-key-description' and `text-char-description').  These
functions are used primarily for making help messages.

 - Function: char-to-string character
     This function returns a new string containing one character,
     CHARACTER.  This function is semi-obsolete because the function
     `string' is more general.  Note: Creating Strings.

 - Function: string-to-char string
     This function returns the first character in STRING.  If the
     string is empty, the function returns 0.  The value is also 0 when
     the first character of STRING is the null character, ASCII code 0.

          (string-to-char "ABC")
               => 65
          (string-to-char "xyz")
               => 120
          (string-to-char "")
               => 0
          (string-to-char "\000")
               => 0

     This function may be eliminated in the future if it does not seem
     useful enough to retain.

 - Function: number-to-string number
     This function returns a string consisting of the printed base-ten
     representation of NUMBER, which may be an integer or a floating
     point number.  The returned value starts with a minus sign if the
     argument is negative.

          (number-to-string 256)
               => "256"
          (number-to-string -23)
               => "-23"
          (number-to-string -23.5)
               => "-23.5"

     `int-to-string' is a semi-obsolete alias for this function.

     See also the function `format' in Note: Formatting Strings.

 - Function: string-to-number string &optional base
     This function returns the numeric value of the characters in
     STRING.  If BASE is non-`nil', integers are converted in that
     base.  If BASE is `nil', then base ten is used.  Floating point
     conversion always uses 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-number' returns 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.  (On some
     systems it ignores other whitespace at the beginning, not just
     spaces and tabs.)  If the first character after the ignored
     whitespace is neither a digit, nor a plus or minus sign, nor the
     leading dot of a floating point 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

     `string-to-int' is an obsolete alias for this function.

   Here are some other functions that can convert to or from a string:

`concat'
     `concat' can convert a vector or a list into a string.  Note:
     Creating Strings.

`vconcat'
     `vconcat' can convert a string into a vector.  Note: Vector
     Functions.

`append'
     `append' can convert a string into a list.  Note: Building Lists.


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