Info Catalog elisp: Syntax Tables elisp: Syntax Descriptors

elisp: Syntax Basics

 
 34.1 Syntax Table Concepts
 ==========================
 
 A syntax table is a data structure which can be used to look up the
 “syntax class” and other syntactic properties of each character.  Syntax
 tables are used by Lisp programs for scanning and moving across text.
 
    Internally, a syntax table is a char-table (Char-Tables).
 The element at index C describes the character with code C; its value is
 a cons cell which specifies the syntax of the character in question.
 Syntax Table Internals, for details.  However, instead of using
 ‘aset’ and ‘aref’ to modify and inspect syntax table contents, you
 should usually use the higher-level functions ‘char-syntax’ and
 ‘modify-syntax-entry’, which are described in Syntax Table
 Functions.
 
  -- Function: syntax-table-p object
      This function returns ‘t’ if OBJECT is a syntax table.
 
    Each buffer has its own major mode, and each major mode has its own
 idea of the syntax class of various characters.  For example, in Lisp
 mode, the character ‘;’ begins a comment, but in C mode, it terminates a
 statement.  To support these variations, the syntax table is local to
 each buffer.  Typically, each major mode has its own syntax table, which
 it installs in all buffers that use that mode.  For example, the
 variable ‘emacs-lisp-mode-syntax-table’ holds the syntax table used by
 Emacs Lisp mode, and ‘c-mode-syntax-table’ holds the syntax table used
 by C mode.  Changing a major mode’s syntax table alters the syntax in
 all of that mode’s buffers, as well as in any buffers subsequently put
 in that mode.  Occasionally, several similar modes share one syntax
 table.  Example Major Modes, for an example of how to set up a
 syntax table.
 
    A syntax table can “inherit” from another syntax table, which is
 called its “parent syntax table”.  A syntax table can leave the syntax
 class of some characters unspecified, by giving them the “inherit”
 syntax class; such a character then acquires the syntax class specified
 by the parent syntax table (Syntax Class Table).  Emacs defines
 a “standard syntax table”, which is the default parent syntax table, and
 is also the syntax table used by Fundamental mode.
 
  -- Function: standard-syntax-table
      This function returns the standard syntax table, which is the
      syntax table used in Fundamental mode.
 
    Syntax tables are not used by the Emacs Lisp reader, which has its
 own built-in syntactic rules which cannot be changed.  (Some Lisp
 systems provide ways to redefine the read syntax, but we decided to
 leave this feature out of Emacs Lisp for simplicity.)
 

Info Catalog elisp: Syntax Tables elisp: Syntax Descriptors