Re: master ac1d15e95c 1/2: ; * src/data.c (Fash): More precise doc string

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Tue, 19 Jul 2022 19:46:24 +0200
> Cc: emacs-devel@gnu.org
> 
> 19 juli 2022 kl. 17.54 skrev Eli Zaretskii <eliz@gnu.org>:
> 
> > The operation is "bit shift", so
> > the most natural way of describing it is in terms of shifting bits.
> > No?
> 
> Not necessarily. The user inputs numbers and gets a number out, not bit 
> sequences, so it makes sense to describe the behaviour in arithmetic terms. 
> (We're not describing a processor instruction that manipulates registers; 
> `ash` is an operation on mathematical integers.)
> 
> A bitwise description would require knowledge of two's complement 
> representation which you dismissed earlier. If it's acceptable to complement 
> the arithmetic description with something that refers to such representation, 
> then we could have:
> 
>   If we view VALUE as a binary two's complement number, then shifting left 
> introduce new 0-bits to the right and shifting right remove rightmost bits.
>   Since negative numbers have an infinite supply of 1-bits to the left, a 
> negative number remains negative no matter how far it is shifted in either 
> direction.

Sigh.  You know what, forget about this.  I will fix this myself, time
permitting.