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
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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

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