On 14/11/17 13:29, Jonathan Wakely wrote: > On 13 November 2017 at 11:42, Andrew Haley wrote: >> On 13/11/17 10:38, Mason wrote: >>> On 09/11/2017 16:46, Vincent Lefevre wrote: >>> >>>> Actually, that's mainly a language design bug, which doesn't show >>>> the error for 460 (which is representable exactly). >>> >>> It's not clear to me exactly /what/ you are calling a language design bug? >>> And in what language? C? IEEE 754?> (AFAIK, C is pretty loose with the floating point spec.) >> >> This is C++. The problem is that std::cout << v doesn't print all of >> the digits in v: ideally, it'd print the minimum number of digits such >> that reading the number back would result in a double equal to v. > > It might be nice to have that as an option (maybe via an I/O > manipulator like std::fixed) but even if it wasn't too late to change > the default behaviour, most people probably want 1.1 to be printed as > 1.1 even though it's really something different. 1.1 would still print as 1.1. 4.6 * 100 would print as 459.99999999999994, because that's the truth. -- Andrew Haley Java Platform Lead Engineer Red Hat UK Ltd. <https://www.redhat.com> EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671
