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Re: beginning-of-buffer computations
From: |
Robert Thorpe |
Subject: |
Re: beginning-of-buffer computations |
Date: |
Sun, 01 Feb 2015 14:42:24 +0000 |
Marcin Borkowski <mbork@wmi.amu.edu.pl> writes:
> (/ (+ 10 (* size (prefix-numeric-value arg))) 10)))
This line was in the first version of simple.el put into revision
control in 1991. I think the aim was to prevent a calculation like (/ 0
10). On some platforms it's an error to divide zero by anything, and it
triggers an interrupt. Perhaps that was a problem at the time.
That leaves the question: why is the calculation done this way? I think
that's because not all Emacs version supported floating point at the
time. I think in that case numbers described by ratios were used
instead, e.g. 5/6.
I'm not sure on either of these things though.
> (Not to mention the next line - not shown here - which `forward-line's
> by 1. Why not just (beginning-of-line) instead?)
I think that's because of "field text motion". See the help for
beginning-of-line.
BR,
Robert Thorpe