Xref:	news2.mv.net comp.lang.c:54496 comp.lang.c++:69991 comp.os.msdos.djgpp:675 gnu.g++.help:4433 gnu.gcc.help:5648
Newsgroups:	comp.lang.c,comp.lang.c++,gnu.gcc.help,gnu.g++.help,comp.os.msdos.djgpp
Subject:	Re: float != float and floats as return types
Message-ID:	<DM04ur.I6u@cwi.nl>
From:	dik AT cwi DOT nl (Dik T. Winter)
Date:	Tue, 30 Jan 1996 16:08:50 GMT
Sender:	news AT cwi DOT nl (The Daily Dross)
References:	<4ej9lb$mpc AT fu-berlin DOT de>
Organization:	CWI, Amsterdam
Nntp-Posting-Host:	chrysant.cwi.nl
Lines:	24
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

In article <4ej9lb$mpc AT fu-berlin DOT de> axl AT zedat DOT fu-berlin DOT de writes:
 > Hello,
 > I am getting confused, about how C/C++ manage float binary operations,
 > in particular multiplication. The next C++ example gives me surprising
 > results:
.....
 > 	float quad( float );
.....
 > 	    a = i/13.123123;
 > 	    b = a*a;
 > 	    c = quad(a);
 > 	    cout << (b - c) << '\t';
 > 	    cout << (b - a*a) << '\t';
 > 	    cout << (c - quad(a)) << '\n';

Declaring a function as returning float does not imply that the actual
value returned is indeed a float!  In K&R times expressions involving
floats were calculated using doubles.  Some compilers extended that
to functions declared as returning float: a double result was returned;
others did indeed truncate the return value to float.  Thorough
reading of K&R does not lead to a clear solution here.  In ANSI C both
are allowed.
-- 
dik t. winter, cwi, kruislaan 413, 1098 sj  amsterdam, nederland, +31205924098

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