C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  primitive range          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message John Ratliff Guest Posted: Wed Sep 28, 2005 11:29 pm    Post subject: primitive range Is there a guaranteed minimum size for the primitive double? I need to know if I can store 5.12 * 2^32 - 1 in a double. http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.5 Only talks about minimum sizes for integer values. It doesn't say anything about float or double. Thanks, --John Ratliff Back to top Mark P Guest Posted: Thu Sep 29, 2005 12:01 am    Post subject: Re: primitive range John Ratliff wrote: Quote: Is there a guaranteed minimum size for the primitive double? I need to know if I can store 5.12 * 2^32 - 1 in a double. http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.5 Only talks about minimum sizes for integer values. It doesn't say anything about float or double. Thanks, --John Ratliff Not sure if this fits the bill, but you may want to check numeric_limits<double>::epsilon defined in <limits> Back to top red floyd Guest Posted: Thu Sep 29, 2005 12:57 am    Post subject: Re: primitive range John Ratliff wrote: Quote: Is there a guaranteed minimum size for the primitive double? I need to know if I can store 5.12 * 2^32 - 1 in a double. http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.5 Only talks about minimum sizes for integer values. It doesn't say anything about float or double. Thanks, --John Ratliff The standard says that the rep for a floating point value is implementation defined (3.9.1/. It also says to use std::numeric_limits<> (18.2) for any given type. However most implementations of double that I've seen use IEEE 64 bit rep (1 sign, 10 bit exponent, 53 bit normalized mantissa). The real so a double probably could. The other issue is that I'm not sure that 5.12 is exactly representable as a double (It may be an infinitely recurring binary fraction). Back to top John Ratliff Guest Posted: Thu Sep 29, 2005 3:55 am    Post subject: Re: primitive range red floyd wrote: Quote: John Ratliff wrote: Is there a guaranteed minimum size for the primitive double? I need to know if I can store 5.12 * 2^32 - 1 in a double. http://www.parashift.com/c++-faq-lite/newbie.html#faq-29.5 Only talks about minimum sizes for integer values. It doesn't say anything about float or double. Thanks, --John Ratliff The standard says that the rep for a floating point value is implementation defined (3.9.1/. It also says to use std::numeric_limits<> (18.2) for any given type. However most implementations of double that I've seen use IEEE 64 bit rep (1 sign, 10 bit exponent, 53 bit normalized mantissa). The real so a double probably could. The other issue is that I'm not sure that 5.12 is exactly representable as a double (It may be an infinitely recurring binary fraction). Okay. This is my test progam. I get the right value, but I want to make sure my conversion is okay. #include <cmath> #include <iostream> int main(int, char **) { double factor = 256.0 / 50.0; double time = (0xFFFFFFFF * factor); double temp; temp = time / 3600; std::cout << "hours = " << static_cast temp = fmod(time / 60, 60); std::cout << "minutes = " << static_cast temp = fmod(time, 60); if ((temp - floor(temp)) >= 0.5) ++temp; std::cout << "seconds = " << static_cast return 0; } When I round the seconds, will that be valid, or do I need to do something more like: if ((floor((temp - floor(temp)) * 10) / 10) >= 0.5) ++temp; Thanks, --John Ratliff 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.