Re: [Boost-users] Ann: Floating Point Utilities Review starts today

From: Matt Gruenke (mgruenke_at_[hidden])
Date: 2008-03-03 22:46:48

To access the native binary representation of floating-point type T, 
isn't it easier & safer to use a union of T and a character array with 
sizeof (T) elements?

Matt

Pfligersdorffer, Christian wrote:
> Hello all,
>
> we use fp_utilities in our portable binary archive implementation to
> serialize floating point numbers. For doing so we found the functions
> fp_traits<T>_impl::get_bits() and set_bits() to be exactly what we need.
> In combination with Beman Dawes endian library we're able to transfer
> binary data between ppc-32 and x86-32 reliably. This might serve as a
> usecase since John Maddock pointed out serialization as a prominent
> application of the library.
>
> /**
>  * save floating point types
>  * 
>  * We simply rely on fp_traits to extract the bit pattern into an
> (unsigned)
>  * integral type and store that into the stream.
>  *
>  * \todo treat nan values using fp_classify
>  */
> template <typename T>
> BOOST_DEDUCED_TYPENAME boost::enable_if<boost::is_floating_point<T>
>   
>> ::type
>>     
> save(const T & t, dummy<3> = 0)
> {
> 	using namespace boost::math::detail;
> 	BOOST_DEDUCED_TYPENAME fp_traits<T>::type::bits bits;
> 	fp_traits<T>::type::get_bits(t, bits);
> 	save(bits);
> }
>
> As you can see our code depends on functions that apparently are not
> part of the public interface and I wonder why. Perhaps I overlooked
> something? Those interested in the full code can find it in the boost
> vault.
>
> To sum it up: We think the fp_utilities provide useful functionality and
> our tests indicate reliability that can be counted on. So thank you
> Johan Rade for this contribution!
>
>
> Best Regards,
>
> --
> Christian Pfligersdorffer
> Software Engineering
> http://www.eos.info
>  
>
> John Maddock wrote:
>
>   
>> The review of Johan Rade's floating point utilities starts today.
>>
>> [...]
>>
>> 3) C++ locale facets: these will read and write non-finite
>> numbers in a portable and round-trippable way: that is not
>> otherwise possible with current C++ std library
>> implementations.  These are particularly useful for
>> number-serialisation for example.
>>
>> Since the design is already specified by the C++ standard for
>> these facets, your review here should focus on
>> implementation, testing, documentation, and perhaps where in
>> Boost these should best be placed if accepted.
>>
>> These look to be a useful collection of utilities, so I'll
>> look forward to your reviews,
>>     
>
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