Mail Archives: djgpp/1997/10/18/17:31:18

From: Jonathan Foster <jgf1 AT ukc DOT ac DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Newbie seeks help with rotating triangle program
Date: Wed, 15 Oct 1997 16:38:12 +0100
Organization: University of Kent at Canterbury, England
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Message-ID: <>
References: <19971015041101 DOT AAA17302 AT ladder01 DOT news DOT aol DOT com>
Mime-Version: 1.0
To: djgpp AT delorie DOT com
DJ-Gateway: from newsgroup comp.os.msdos.djgpp

Joshua Hab wrote:
> x=(RADIUS_LENGTH*(cos(theta/360*6.28)))+CENTER_X

This is a problem with number types.  The fragment "theta/360" is
taking an "int theta" and dividing it by the integer 360.  The result
will be rounded to an _integer_ according to the ANSI C spec, and
because the answer is less than 1 this means the angle will always be
rounded to zero.

Try this:  "theta/360.0*6.28"  The "360.0" is now a _float_, so the
value of "theta" is made into a float.  This allows the division to 
give a fractional answer, and it should work.

   Jon Foster.

(1st Year Maths/Computer Science Student)

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