[v3] complex functions with expression template reals

[Paolo Carlini]

Hi,

On 02/23/2014 04:11 PM, Marc Glisse wrote:
> On Sun, 23 Feb 2014, Paolo Carlini wrote:
>
>> On 02/23/2014 11:32 AM, Marc Glisse wrote:
>>> Hello,
>>>
>>> looking at this question:
>>> http://stackoverflow.com/q/21737186/1918193
>>> I was surprised to see that libstdc++'s std::complex basically just 
>>> works with user-defined types, even weird expression template ones, 
>>> although that's not a supported use afaik.
>>>
>>> The only functions that fail seem to be exp and pow, both because 
>>> they call polar with two arguments that have different (expression) 
>>> types.
>>>
>>> I am not proposing to make this a supported use, but the cost of 
>>> this small patch seems very low, and if it makes a couple users 
>>> happy...
>>>
>>> Regtested with no problem on x86_64-linux-gnu, ok for stage 1?
>>
>> I would even be in favor of applying it now. Can we figure out simple 
>> (ie, not relying on boost...) testcases too?
>
> I didn't try std::complex<std::valarray<X>>, maybe...
>
> Otherwise, you need a type T with all the (real) math functions 
> defined, and where every operation returns a different type 
> (implicitly convertible to T). And then you want to call all the 
> complex functions.
>
> That seems doable, but way bigger than I'm willing to go for this 
> feature. If you want to take over, be my guest ;-)
Another option would be just using boost/multiprecision/mpfr.hpp when 
available. In general, I think it makes sense to have a minimum of 
infrastructure enabling tests checking interoperability with boost. If 
only we had a check_v3_target_header { args } it would be most of it, 
but it doesn't seem we do?!? Anyway I guess we can take care of that 
post 4.9.0 and commit the straightforward code tweak now. Jon?

Paolo.

PS: Resending message, yesterday had issues with html