Info Catalog elisp: Non-ASCII in Strings elisp: String Type elisp: Text Props and Strings

elisp: Nonprinting Characters

 
 2.3.8.3 Nonprinting Characters in Strings
 .........................................
 
 You can use the same backslash escape-sequences in a string constant as
 in character literals (but do not use the question mark that begins a
 character constant).  For example, you can write a string containing the
 nonprinting characters tab and ‘C-a’, with commas and spaces between
 them, like this: ‘"\t, \C-a"’.  Character Type, for a
 description of the read syntax for characters.
 
    However, not all of the characters you can write with backslash
 escape-sequences are valid in strings.  The only control characters that
 a string can hold are the ASCII control characters.  Strings do not
 distinguish case in ASCII control characters.
 
    Properly speaking, strings cannot hold meta characters; but when a
 string is to be used as a key sequence, there is a special convention
 that provides a way to represent meta versions of ASCII characters in a
 string.  If you use the ‘\M-’ syntax to indicate a meta character in a
 string constant, this sets the 2**7 bit of the character in the string.
 If the string is used in ‘define-key’ or ‘lookup-key’, this numeric code
 is translated into the equivalent meta character.  Character
 Type.
 
    Strings cannot hold characters that have the hyper, super, or alt
 modifiers.
 

Info Catalog elisp: Non-ASCII in Strings elisp: String Type elisp: Text Props and Strings