Info Catalog elisp: Substitution elisp: Text elisp: Transposition

elisp: Registers

 
 31.21 Registers
 ===============
 
 A register is a sort of variable used in Emacs editing that can hold a
 variety of different kinds of values.  Each register is named by a
 single character.  All ASCII characters and their meta variants (but
 with the exception of ‘C-g’) can be used to name registers.  Thus, there
 are 255 possible registers.  A register is designated in Emacs Lisp by
 the character that is its name.
 
  -- Variable: register-alist
      This variable is an alist of elements of the form ‘(NAME .
      CONTENTS)’.  Normally, there is one element for each Emacs register
      that has been used.
 
      The object NAME is a character (an integer) identifying the
      register.
 
    The CONTENTS of a register can have several possible types:
 
 a number
      A number stands for itself.  If ‘insert-register’ finds a number in
      the register, it converts the number to decimal.
 
 a marker
      A marker represents a buffer position to jump to.
 
 a string
      A string is text saved in the register.
 
 a rectangle
      A rectangle is represented by a list of strings.
 
 ‘(WINDOW-CONFIGURATION POSITION)’
      This represents a window configuration to restore in one frame, and
      a position to jump to in the current buffer.
 
 ‘(FRAME-CONFIGURATION POSITION)’
      This represents a frame configuration to restore, and a position to
      jump to in the current buffer.
 
 (file FILENAME)
      This represents a file to visit; jumping to this value visits file
      FILENAME.
 
 (file-query FILENAME POSITION)
      This represents a file to visit and a position in it; jumping to
      this value visits file FILENAME and goes to buffer position
      POSITION.  Restoring this type of position asks the user for
      confirmation first.
 
    The functions in this section return unpredictable values unless
 otherwise stated.
 
  -- Function: get-register reg
      This function returns the contents of the register REG, or ‘nil’ if
      it has no contents.
 
  -- Function: set-register reg value
      This function sets the contents of register REG to VALUE.  A
      register can be set to any value, but the other register functions
      expect only certain data types.  The return value is VALUE.
 
  -- Command: view-register reg
      This command displays what is contained in register REG.
 
  -- Command: insert-register reg &optional beforep
      This command inserts contents of register REG into the current
      buffer.
 
      Normally, this command puts point before the inserted text, and the
      mark after it.  However, if the optional second argument BEFOREP is
      non-‘nil’, it puts the mark before and point after.
 
      When called interactively, the command defaults to putting point
      after text, and a prefix argument inverts this behavior.
 
      If the register contains a rectangle, then the rectangle is
      inserted with its upper left corner at point.  This means that text
      is inserted in the current line and underneath it on successive
      lines.
 
      If the register contains something other than saved text (a string)
      or a rectangle (a list), currently useless things happen.  This may
      be changed in the future.
 
  -- Function: register-read-with-preview prompt
      This function reads and returns a register name, prompting with
      PROMPT and possibly showing a preview of the existing registers and
      their contents.  The preview is shown in a temporary window, after
      the delay specified by the user option ‘register-preview-delay’, if
      its value and ‘register-alist’ are both non-‘nil’.  The preview is
      also shown if the user requests help (e.g., by typing the help
      character).  We recommend that all interactive commands which read
      register names use this function.
 

Info Catalog elisp: Substitution elisp: Text elisp: Transposition