Info Catalog eintr: beginning-of-buffer opt arg eintr: beginning-of-buffer

eintr: beginning-of-buffer complete

 
 5.3.3 The Complete ‘beginning-of-buffer’
 ----------------------------------------
 
 Here is the complete text of the ‘beginning-of-buffer’ function:
 
      (defun beginning-of-buffer (&optional arg)
        "Move point to the beginning of the buffer;
      leave mark at previous position.
      With \\[universal-argument] prefix,
      do not set mark at previous position.
      With numeric arg N,
      put point N/10 of the way from the beginning.
 
      If the buffer is narrowed,
      this command uses the beginning and size
      of the accessible part of the buffer.
 
      Don't use this command in Lisp programs!
      \(goto-char (point-min)) is faster
      and avoids clobbering the mark."
        (interactive "P")
        (or (consp arg)
            (and transient-mark-mode mark-active)
            (push-mark))
        (let ((size (- (point-max) (point-min))))
          (goto-char (if (and arg (not (consp arg)))
                         (+ (point-min)
                            (if (> size 10000)
                                ;; Avoid overflow for large buffer sizes!
                                (* (prefix-numeric-value arg)
                                   (/ size 10))
                              (/ (+ 10 (* size (prefix-numeric-value arg)))
                                 10)))
                       (point-min))))
        (if (and arg (not (consp arg))) (forward-line 1)))
 
 Except for two small points, the previous discussion shows how this
 function works.  The first point deals with a detail in the
 documentation string, and the second point concerns the last line of the
 function.
 
    In the documentation string, there is reference to an expression:
 
      \\[universal-argument]
 
 A ‘\\’ is used before the first square bracket of this expression.  This
 ‘\\’ tells the Lisp interpreter to substitute whatever key is currently
 bound to the ‘[...]’.  In the case of ‘universal-argument’, that is
 usually ‘C-u’, but it might be different.  (Tips for Documentation
 Strings (elisp)Documentation Tips, for more information.)
 
    Finally, the last line of the ‘beginning-of-buffer’ command says to
 move point to the beginning of the next line if the command is invoked
 with an argument:
 
      (if (and arg (not (consp arg))) (forward-line 1))
 
 This puts the cursor at the beginning of the first line after the
 appropriate tenths position in the buffer.  This is a flourish that
 means that the cursor is always located _at least_ the requested tenths
 of the way through the buffer, which is a nicety that is, perhaps, not
 necessary, but which, if it did not occur, would be sure to draw
 complaints.  (The ‘(not (consp arg))’ portion is so that if you specify
 the command with a ‘C-u’, but without a number, that is to say, if the
 raw prefix argument is simply a cons cell, the command does not put you
 at the beginning of the second line.)
 

Info Catalog eintr: beginning-of-buffer opt arg eintr: beginning-of-buffer