C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Value of INF (double)          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Rob.Meyer1@gmail.com Guest Posted: Tue Sep 27, 2005 11:02 pm    Post subject: Value of INF (double) I'm working on a class for working with fractions and one of the public functions is to return the decimal value of the fraction which is simple enough except for when the denominator is 0. I don't want to return 0.0 because thats not what it is, I would rather return NaN or INF but I can't figure out how to do that. Does anyone know the expression for either of these in doubles? Or even the bit pattern that represents INF and/or NaN? I can't seem to find it posted anywhere. double Fraction::Decimal() const{ if (IsValid()) return double(n) / d; else return ???; } //n is numerator, d is denominator, of course. ??? is the expression I need to figure out. Back to top Pete Becker Guest Posted: Tue Sep 27, 2005 11:08 pm    Post subject: Re: Value of INF (double) [email]Rob.Meyer1 (AT) gmail (DOT) com[/email] wrote: Quote: I would rather return NaN or INF but I can't figure out how to do that. They mean very different things. But unless you're talking about 0.0/0.0. the correct value is infinity, not NaN. Quote: Does anyone know the expression for either of these in doubles? numeric_limits<double>::infinity() and numeric_limits<double>::quite_NaN(). -- Pete Becker Dinkumware, Ltd. (http://www.dinkumware.com) Back to top Pete Becker Guest Posted: Tue Sep 27, 2005 11:28 pm    Post subject: Re: Value of INF (double) Pete Becker wrote: Quote: numeric_limits<double>::quite_NaN(). Of course, that should be numeric_limits<double>::quiet_NaN(). -- Pete Becker Dinkumware, Ltd. (http://www.dinkumware.com) Back to top Rob.Meyer1@gmail.com Guest Posted: Wed Sep 28, 2005 12:04 am    Post subject: Re: Value of INF (double) I'm having some troubles getting that to compile, here's what i've got now: double Fraction::Decimal() const{ if (d != 0) //return decimal equivelent return double(n) / d; else if (n != 0) //return INF return numeric_limits<double>::infinity(); else //return NaN return numeric_limits<double>::quiet_NaN(); } The errors I am getting are: error C2039: 'infinity' : is not a member of 'operator``global namespace''' error C2039: 'quiet_NaN' : is not a member of 'operator``global namespace''' error C2062: type 'double' unexpected error C2062: type 'double' unexpected error C2065: 'numeric_limits' : undeclared identifier The first two are on the lines you would expect, type double errors are on lines 7 and 10 (from code above) and I find it odd that the last error only appears once and not twice, it points to line 7. I'm guessing I slaughtered the code pretty bad, I've never messed around with calling some barely heard-of function in a standard library somewhere. I would have guessed it would be included in iostream somewhere, maybe not? Thanks for the help in advance, would be nice to know how to get this one working. Back to top Ali Çehreli Guest Posted: Wed Sep 28, 2005 12:16 am    Post subject: Re: Value of INF (double) <Rob.Meyer1 (AT) gmail (DOT) com> wrote Quote: I'm having some troubles getting that to compile, here's what i've got now: double Fraction::Decimal() const{ if (d != 0) //return decimal equivelent return double(n) / d; else if (n != 0) //return INF return numeric_limits<double>::infinity(); else //return NaN return numeric_limits<double>::quiet_NaN(); } The errors I am getting are: error C2039: 'infinity' : is not a member of 'operator``global namespace''' error C2039: 'quiet_NaN' : is not a member of 'operator``global namespace''' error C2062: type 'double' unexpected error C2062: type 'double' unexpected error C2065: 'numeric_limits' : undeclared identifier The error messages are not very helpful, but are probably due to the fact that <limits> is not included. This should work: #include <limits> using std::numeric_limits; double Decimal() { return numeric_limits<double>::infinity(); } int main() { Decimal(); } Ali Back to top Pete Becker Guest Posted: Wed Sep 28, 2005 12:44 am    Post subject: Re: Value of INF (double) [email]Rob.Meyer1 (AT) gmail (DOT) com[/email] wrote: Quote: I would have guessed it would be included in iostream somewhere, maybe not? Don't guess. Look it up. That's what the documentation is for. -- Pete Becker Dinkumware, Ltd. (http://www.dinkumware.com) Back to top Walter Bright Guest Posted: Wed Sep 28, 2005 1:38 am    Post subject: Re: Value of INF (double) <Rob.Meyer1 (AT) gmail (DOT) com> wrote Quote: I'm working on a class for working with fractions and one of the public functions is to return the decimal value of the fraction which is simple enough except for when the denominator is 0. I don't want to return 0.0 because thats not what it is, I would rather return NaN or INF but I can't figure out how to do that. Does anyone know the expression for either of these in doubles? Or even the bit pattern that represents INF and/or NaN? I can't seem to find it posted anywhere. If you're using Digital Mars C/C++ or any compiler with a C99 conformant math.h header file: #include <math.h> INFINITY for infinity NAN for nan Not all floating point implementations support the notion of INFINITY or NAN. -Walter www.digitalmars.com C, C++, D programming language compilers Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.