Path: chuka.playstation.co.uk!tjs
From: tjs@cs.monash.edu.au (Toby Sargeant)
Newsgroups: scee.yaroze.beginners
Subject: Re: Clever bit manipulation routines?
Date: 24 Jul 1998 03:53:11 GMT
Organization: PlayStation Net Yaroze (SCEE)
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On 24 Jul 1998 12:05:57 +1000, Toby Hutton <thutton@cybec.com.au> wrote:
[snip]
>The libraries often use 12 bit fixed point math.  This means that 4096
>is 1, 2048 is 1/2 and 512 will be an eighth.  512 in hex is 0x0200 and
>511 is 0x01ff.  To limit a value between 0 and +511 you simply:
>
>val &= 0x1ff;

sadly, that won't do what was wanted. That will wrap all values into a range,
whereas the intention was to compute f(x), where f(x)=-45 if x<-45, f(x)=x
if -45<=x<=45, f(x)=45 if 45<x.

while you could do that with bitops, it would be messier and slower than the
equivalent test/assigns.

toby.