-----Original Message----- From: Boost [mailto:boost-bounces@lists.boost.org] On Behalf Of Christopher Kormanyos Sent: Monday, March 18, 2013 9:46 PM To: boost@lists.boost.org Subject: [boost] [math] Extended float in C++ : Was : Support for libquadmath/ __float128
There has been some recent discussion on extended floating-point types in C++.
So the only way to add Q or q suffixes would be to find a way to query
the environment if it is supported. I wonder if GCC with --enable-libquadmath has a kind of query for this.
I haven't found one - gcc-4.7.2 has all sorts of __SIZEOF_XXX__ defines for every last type *except* __float128 and __float80 :-(
It won't help now, but is 'more precise types' an issue to raise with WG21 for the next C++ standard? Or is Multiprecision the way to go?
Is there any definitive interest in adding more precise floating-point types to C++ in the next draft?
Here, I am talking about floating-point types with fixed precision such as 24, 54, 113 or more binary digits, and possibly even extending beyond these to potential multiprecision types.
See also Boost.Multiprecision.
Consider the C language in ISO/IEC 9899:2011 (in other words C11). Extended precision is not specified, but there is a remark in Section 6.11.1:
"Future standardization may include additional floating-point types, including those with greater range, precision, or both than long double."
Recent specification of fixed-size integer types in C99, C11 and C++11 has drastically improved integer algorithm portability and range.
Similar specification of fixed-size floating-point types could potentially improve the C++ language significantly, especially in the scientific and engineering communities.
One could envision two ways to go:
* Types such as float24_t, float53_t, float113_t, ... * Types such as float32_t, float64_t, float128_t, ...The first set above is intuitively coined from IEE754:2008. It is also consistent with the gist of std::uint32_t, et al --- in so far as the number of binary digits of precision is contained within the name of the data type.
Is there any interest in committing to this project? Specification takes a long time and requires a coalition of collaborators. I could potentially contribute to this project as a subordinate author. But I don't feel confident enough to champion such a cause.
I think that, although fixed/higher-precisions is a 'niche market', they are 'killer' features for some would-be C++ users. So I would strongly support these additions and am willing to contribute what I can. Preparing a draft 'N' paper for discussion here would be a start, with some use cases demos, and then submission to WG21 for their consideration. The wording of std::uint32_t will provide a Standardese template? Paul --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow@hetp.u-net.com