C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Negative Infinity          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message David Sachs Guest Posted: Sat Apr 08, 2006 5:06 pm    Post subject: Negative Infinity What is the C++ standard way to return a value of Negative Infinity? While the IEEE floating point standard provides for both positive and negative infinity, the C++ standard header provides only for Positive infinity. The negative infinity value is needed as the minimum value for a distribution that covers the entire real number range. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Guest Posted: Sat Apr 08, 2006 7:06 pm    Post subject: Re: Negative Infinity "David Sachs" wrote: Quote: What is the C++ standard way to return a value of Negative Infinity? While the IEEE floating point standard provides for both positive and negative infinity, the C++ standard header provides only for Positive infinity. The C++ standard deliberately doesn't say much about details like this, leaving it for other standards to cover, such as IEC 559 (which is the same as IEEE 754). If std::numeric_limits<T>::is_iec559 is true, then IEC 559 is supposed to apply, and therefore -std::numeric_limits<T>::infinity() should give you a negative infinity. It's probably also true if is_iec559 is false, since that's a very reasonable result, but you have no guarantees in that case. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Tomás Guest Posted: Sat Apr 08, 2006 10:06 pm    Post subject: Re: Negative Infinity "David Sachs" posted: Quote: What is the C++ standard way to return a value of Negative Infinity? While the IEEE floating point standard provides for both positive and negative infinity, the C++ standard header provides only for Positive infinity. The negative infinity value is needed as the minimum value for a distribution that covers the entire real number range. Have you tried: double positive_infinity = ... double negative_infinity = -positive_infinity; -Tomás --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top P.J. Plauger Guest Posted: Sat Apr 08, 2006 10:06 pm    Post subject: Re: Negative Infinity ""David Sachs"" <sachs (AT) fnal (DOT) gov> wrote in message news:DY6dnSFL2JsNharZRVn-ug (AT) comcast (DOT) com... Quote: What is the C++ standard way to return a value of Negative Infinity? While the IEEE floating point standard provides for both positive and negative infinity, the C++ standard header provides only for Positive infinity. The negative infinity value is needed as the minimum value for a distribution that covers the entire real number range. Try -std::numeric_limits<double>::infinity(). You have to first include <limits>. P.J. Plauger Dinkumware, Ltd. http://www.dinkumware.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top David Sachs Guest Posted: Sun Apr 09, 2006 4:06 am    Post subject: Re: Negative Infinity ""P.J. Plauger"" <pjp (AT) dinkumware (DOT) com> wrote in message news:3v6dnVE8n8ennKXZRVn-vQ (AT) giganews (DOT) com... Quote: ""David Sachs"" <sachs (AT) fnal (DOT) gov> wrote in message news:DY6dnSFL2JsNharZRVn-ug (AT) comcast (DOT) com... What is the C++ standard way to return a value of Negative Infinity? While the IEEE floating point standard provides for both positive and negative infinity, the C++ standard header provides only for Positive infinity. The negative infinity value is needed as the minimum value for a distribution that covers the entire real number range. Try -std::numeric_limits<double>::infinity(). You have to first include <limits>. P.J. Plauger Dinkumware, Ltd. http://www.dinkumware.com "-std::numeric_limits<TYPE>::infinity()" is what I did use. It works with GCC, and probably with any IEEE conforming floating point re[resentation, but I could not find anything that guarantees its conformance with the C++ standard. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top P.J. Plauger Guest Posted: Mon Apr 10, 2006 12:06 am    Post subject: Re: Negative Infinity ""David Sachs"" <sachs (AT) fnal (DOT) gov> wrote in message news:4s6dnZ5lMf_M9KXZnZ2dnUVZ_uidnZ2d (AT) comcast (DOT) com... Quote: ""P.J. Plauger"" <pjp (AT) dinkumware (DOT) com> wrote in message news:3v6dnVE8n8ennKXZRVn-vQ (AT) giganews (DOT) com... ""David Sachs"" <sachs (AT) fnal (DOT) gov> wrote in message news:DY6dnSFL2JsNharZRVn-ug (AT) comcast (DOT) com... What is the C++ standard way to return a value of Negative Infinity? While the IEEE floating point standard provides for both positive and negative infinity, the C++ standard header provides only for Positive infinity. The negative infinity value is needed as the minimum value for a distribution that covers the entire real number range. Try -std::numeric_limits<double>::infinity(). You have to first include <limits>. P.J. Plauger Dinkumware, Ltd. http://www.dinkumware.com "-std::numeric_limits<TYPE>::infinity()" is what I did use. It works with GCC, and probably with any IEEE conforming floating point re[resentation, but I could not find anything that guarantees its conformance with the C++ standard. Conform in what way? Certainly the reference to numeric_limits is conforming. Whether it can deliver a true infinity depends on the underlying representation for floating point. Perhaps you're worried that you can't negate infinity -- well, in IEC 60559 (IEEE/754) you can. P.J. Plauger Dinkumware, Ltd. http://www.dinkumware.com --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. 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