Path: chuka.playstation.co.uk!news
From: Nick Slaven <NickSlaven@compuserve.com>
Newsgroups: scee.yaroze.beginners
Subject: Re: Clever bit manipulation routines?
Date: Thu, 23 Jul 1998 23:38:41 +0100
Organization: PlayStation Net Yaroze (SCEE)
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Philip Gooch wrote:
> 
> Hello folks
> 
> I've got a few lines of code that look ugly and wondered if there's a
> clever bit manipulation routine using shifting, ANDing and complement or
> something to achieve the same thing. I'm sure there's a way, just can't
> figure it out.
> 
> Basically:
> 
> if (gPlayer.turningAngle > 45) gPlayer.turningAngle = 45;
> if (gPlayer.turningAngle < -45) gPlayer.turningAngle = -45;
> 
> I'm convinced there's something out there that will handle both of these
> in one line, something like
> (~(gPlayer.turningAngle) & 0x2d) >> something. Though obviously not
> this!
> 
> Do you see what I'm getting at? Something that will leave the variable
> unchanged unless it is greater or less than a certain value, in which
> case it becomes that value.
> 
> Anyone have any ideas?
> 
> Cheers
> 
> Phil
how about the limitRange macro (tho its not bit manipulation)
like this

limitRange(gPlayer.turningAngle,-45,45);

its defined in libps.h & is coded as follows.

#define limitRange(x, l, h)	((x)=((x)<(l)?(l):(x)>(h)?(h):(x)))

The A=B?C:D; construct you find here, (if you're familiar with it
ignore the rest) takes the argument in B and if it is nonzero (ie true)
sticks the value of C in A, if B is zero (ie false) the value of D is 
placed in A. B can be a single variable or any logical expression (like 
(gPlayer.turningAngle<-45) for instance)

cheers

Nick (S)