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

eintr: Disentangle beginning-of-buffer

 
 Disentangle ‘beginning-of-buffer’
 .................................
 
 Like other complex-looking expressions, the conditional expression
 within ‘beginning-of-buffer’ can be disentangled by looking at it as
 parts of a template, in this case, the template for an if-then-else
 expression.  In skeletal form, the expression looks like this:
 
      (if (BUFFER-IS-LARGE
          DIVIDE-BUFFER-SIZE-BY-10-AND-MULTIPLY-BY-ARG
        ELSE-USE-ALTERNATE-CALCULATION
 
    The true-or-false-test of this inner ‘if’ expression checks the size
 of the buffer.  The reason for this is that the old version 18 Emacs
 used numbers that are no bigger than eight million or so and in the
 computation that followed, the programmer feared that Emacs might try to
 use over-large numbers if the buffer were large.  The term “overflow”,
 mentioned in the comment, means numbers that are over large.  More
 recent versions of Emacs use larger numbers, but this code has not been
 touched, if only because people now look at buffers that are far, far
 larger than ever before.
 
    There are two cases: if the buffer is large and if it is not.
 

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