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Xref: | news2.mv.net comp.lang.c:56546 comp.lang.c++:72614 comp.os.msdos.djgpp:1125 gnu.g++.help:4634 gnu.gcc.help:5826 |
From: | rfg AT monkeys DOT com (Ronald F. Guilmette) |
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 |
Date: | 15 Feb 1996 01:15:26 -0800 |
Organization: | Infinite Monkeys & Co. |
Lines: | 37 |
Message-ID: | <4futje$6a4@segfault.monkeys.com> |
References: | <4ej9lb$mpc AT fu-berlin DOT de> <DM04ur DOT I6u AT cwi DOT nl> |
NNTP-Posting-Host: | segfault.monkeys.com |
To: | djgpp AT delorie DOT com |
DJ-Gateway: | from newsgroup comp.os.msdos.djgpp |
In article <DM04ur DOT I6u AT cwi DOT nl>, Dik T. Winter <dik AT cwi DOT nl> wrote: >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! Yes, it does. Please check the ISO C standard and all relevant Committee responses to official Defect Reports before making incorrect claims. >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. That is simply untrue. -- -- Ron Guilmette, Roseville, CA -------- Infinite Monkeys & Co. ------------ ---- E-mail: rfg AT monkeys DOT com ----------- Purveyors of Compiler Test Suites - ------ Copyright (c) 1996 by Ronald F. Guilmette; All rights reserved. -----
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