Info Catalog elisp: Syntax Basics elisp: Syntax Tables elisp: Syntax Table Functions

elisp: Syntax Descriptors

 
 34.2 Syntax Descriptors
 =======================
 
 The “syntax class” of a character describes its syntactic role.  Each
 syntax table specifies the syntax class of each character.  There is no
 necessary relationship between the class of a character in one syntax
 table and its class in any other table.
 
    Each syntax class is designated by a mnemonic character, which serves
 as the name of the class when you need to specify a class.  Usually,
 this designator character is one that is often assigned that class;
 however, its meaning as a designator is unvarying and independent of
 what syntax that character currently has.  Thus, ‘\’ as a designator
 character always stands for escape character syntax, regardless of
 whether the ‘\’ character actually has that syntax in the current syntax
 table.  Syntax Class Table, for a list of syntax classes and
 their designator characters.
 
    A “syntax descriptor” is a Lisp string that describes the syntax
 class and other syntactic properties of a character.  When you want to
 modify the syntax of a character, that is done by calling the function
 ‘modify-syntax-entry’ and passing a syntax descriptor as one of its
 arguments (Syntax Table Functions).
 
    The first character in a syntax descriptor must be a syntax class
 designator character.  The second character, if present, specifies a
 matching character (e.g., in Lisp, the matching character for ‘(’ is
 ‘)’); a space specifies that there is no matching character.  Then come
 characters specifying additional syntax properties (Syntax
 Flags).
 
    If no matching character or flags are needed, only one character
 (specifying the syntax class) is sufficient.
 
    For example, the syntax descriptor for the character ‘*’ in C mode is
 ‘". 23"’ (i.e., punctuation, matching character slot unused, second
 character of a comment-starter, first character of a comment-ender), and
 the entry for ‘/’ is ‘. 14’ (i.e., punctuation, matching character slot
 unused, first character of a comment-starter, second character of a
 comment-ender).
 
    Emacs also defines “raw syntax descriptors”, which are used to
 describe syntax classes at a lower level.  Syntax Table
 Internals.
 

Menu

 
· Syntax Class Table      Table of syntax classes.
· Syntax Flags            Additional flags each character can have.
 

Info Catalog elisp: Syntax Basics elisp: Syntax Tables elisp: Syntax Table Functions