Re: [boost] [math] Support for libquadmath/ __float128

Subject: Re: [boost] [math] Support for libquadmath/ __float128
From: Christopher Kormanyos (e_float_at_[hidden])
Date: 2013-02-24 15:01:55

>>Of course, I made a mistake. You need to qualify the

>>return value with constexpr.
>>
>>template<typename built_in_float_type>
>>constexpr built_in_float_type const_pi()
>>{
>>// This is a true compile-time constant.
>>return 
>>built_in_float_type(3.14159265358979323846264338327950288419716939937511);
>>}
>>

>That only gives you a double precision constant irrespective of the cast,
>John. 

Groan. You're right.

>From ISO/IEC 14882:2011 Sect. 2.14.4:

"The type of a floating literal is double unless explicitly specified
by a suffix. The suffixes f and F specify float, the suffixes l and L
specify long double."

Thanks for the clarification, John.

So this means that the suffixes L and l are the "longest" floating-point
suffixes supported by the language and that the suffixes Q and q are
non-portable language extensions. Is this right?

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.

What a mess! I'm starting to re-remember why I wrote e_float
in the first place.

Best regards, Chris.