Info Catalog elisp: Text Comparison elisp: Strings and Characters elisp: Formatting Strings

elisp: String Conversion

 
 4.6 Conversion of Characters and Strings
 ========================================
 
 This section describes functions for converting between characters,
 strings and integers.  ‘format’ (Formatting Strings) and
 ‘prin1-to-string’ (Output Functions) can also convert Lisp
 objects into strings.  ‘read-from-string’ (Input Functions) can
 convert a string representation of a Lisp object into an object.  The
 functions ‘string-to-multibyte’ and ‘string-to-unibyte’ convert the text
 representation of a string (Converting Representations).
 
    Documentation, for functions that produce textual
 descriptions of text characters and general input events
 (‘single-key-description’ and ‘text-char-description’).  These are used
 primarily for making help messages.
 
  -- Function: number-to-string number
      This function returns a string consisting of the printed base-ten
      representation of 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 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’, 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-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 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
 
      ‘string-to-int’ is an obsolete alias for this function.
 
  -- 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.  Creating Strings.
 
  -- Function: string-to-char string
      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:
 
 ‘concat’
      This function converts a vector or a list into a string.  
      Creating Strings.
 
 ‘vconcat’
      This function converts a string into a vector.  Vector
      Functions.
 
 ‘append’
      This function converts a string into a list.  Building
      Lists.
 
 ‘byte-to-string’
      This function converts a byte of character data into a unibyte
      string.  Converting Representations.
 

Info Catalog elisp: Text Comparison elisp: Strings and Characters elisp: Formatting Strings