From:	Charles Krug <charles AT mail DOT pentek DOT com>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Works on WATCOM, doesn't work on DJGPP?
Date:	Mon, 30 Nov 1998 09:56:14 -0500
Organization:	Pentek Corporation
Lines:	42
Message-ID:	<3662B20E.35394DA5@mail.pentek.com>
References:	<ranla DOT 126 DOT 000B98BD AT post DOT tau DOT ac DOT il>
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To:	djgpp AT delorie DOT com
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Reply-To:	djgpp AT delorie DOT com

Tal Lavi wrote:

> Hello,
>
> I'm using DJGPP 2.81, under DOS.
>
> I wanted to overload the = operator for my fixed point class, as seen in
> another class I download somewhere, that was meant for compiling under WATCOM.
>
> inline fixed &operator= (int a) {value = long(a)<<16;return *this;}
>
> As copied for the class's documentation:
>
> "In general, there are four of each operation , one each for fixed,
> int, float and double. Thankfully, Watcom will automatically cast
> any other ordinal types (short, long, char, unsigned int, etc.) to int."
>
> I was very disapointed to see that DJGPP does not have that quality!
> A simple test program compiles fine when using ints, but gives me errors for
> unknown combination of operands if I use unsigned longs.
>
> Does this is a true DJGPP flaw?

No.  It's a quirk of Watcom's interpretation of the data promotion rules that the class
takes advantage of, but which is NOT guranteed across implementations.

Please consult Stroustroup's, "The C++ Programming Language," section C.6 on implicit
type conversions.  If you don't have a copy, and you plan to work in C++, the go buy
one.


Charles.


--
Charles Krug, Jr.
Application Engineer
Pentek Corp
1 Park Way
Upper Saddle River, NJ 07458

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