From: terra AT diku DOT dk (Morten Welinder)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: math.h sin() function returns wrong value
Date: 12 Jul 1997 23:46:43 GMT
Organization: Department of Computer Science, U of Copenhagen
Lines: 20
Sender: terra AT thor DOT diku DOT dk
Message-ID: <5q9513$84r@vidar.diku.dk>
References: <199707120536 DOT WAA15679 AT adit DOT ap DOT net> <33c7fd44 DOT 36048826 AT news DOT btinternet DOT com>
NNTP-Posting-Host: thor.diku.dk
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp
Precedence: bulk

T DOT Harte AT btinternet DOT com (Thomas Harte) writes:

>#define degtorad(x) (double)x / 180 * PI
>#define radtodeg(x) (double)x / PI * 180

>	. . . although I probably need some brackets, not that I can see where,
>I'm just guessing.

You need them!  Suppose you were to write "degtorad (v + 10)" in your
program.  The compiler would then see "(double)v + 10 / 180 * PI" which
is not quite what you wanted.

Either use an inline function or something like

#define degtorad(x) ((x) / 180.0 * PI)

Morale, if any: always use parenthesis around macro parameters, unless
you are trying to do something you couldn't do with a function.

Morten