Path: utzoo!attcan!uunet!husc6!bloom-beacon!apple!claris!drc
From: drc@claris.UUCP (Dennis Cohen)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Float to integer conversion problem in LSC 3.0?
Keywords: Lightspeed, LSC, conversion
Message-ID: <4571@claris.UUCP>
Date: 8 Aug 88 14:32:38 GMT
References: <5813@batcomputer.tn.cornell.edu>
Reply-To: drc@claris.UUCP (Dennis Cohen)
Organization: Claris Corporation, Mountain View CA
Lines: 26

In article <5813@batcomputer.tn.cornell.edu> eacj@tcgould.tn.cornell.edu (Julian Vrieslander) writes:
>        double d;
>        long m,n;
>	
>        m = 126.0;          /* m becomes 126 */	
>        d = 12.6 * 10.0;    /* d becomes 126 */
>        n = d;              /* n becomes 125 !! */
>		
>I cannot understand why n gets "rounded down" to 125.  Am I missing
>something subtle about C syntax or IEEE type conversions, or is this a bug
>in SANE or LSC?  The variable values shown in the comments were verified
>with the LSC debugger and with my own debugging dialog.  If I use the
>debugger to force a value of 126.0 into d before the last line is
>executed, then n gets the correct result.  What's happening here?    

Well, d is a double that is being assigned the product of two floats, the first
of which does not have an exact binary representation.  Because of this, d will
be 125.999(something).  When you now assign d to n (an integer type) it will
truncate (not round) to make the assignment.  This is not very nice, but it is
"correct" behavior (so far as C, Pascal, and most other languages are
concerned).

Dennis Cohen
Claris Corp.
------------
Disclaimer:  Any opinions expressed above are _MINE_!