Re: problem with changeset fa917f1f0faf

[Ben Abbott]

> On Aug 10, 2016, at 21:29, Carnë Draug <address@hidden> wrote:
> 
> On 11 August 2016 at 01:51, Ben Abbott <address@hidden> wrote:
>>> On Aug 10, 2016, at 8:37 PM, Carnë Draug <address@hidden> wrote:
>>> 
>>>> On 11 August 2016 at 00:47, Ben Abbott <address@hidden> wrote:
>>>> Carne,
>>>> 
>>>> I think I’m seeing an error associated with the change below.
>>>> 
>>>>       http://hg.savannah.gnu.org/hgweb/octave/rev/fa917f1f0faf
>>>> 
>>>> [...]
>>>> 
>>>> liboctave/array/MatrixType.cc:530:23: error: assigning to 'double' from 
>>>> incompatible type 'complex<double>'
>>>>                   d = std::conj (d);
>>>>                     ^ ~~~~~~~~~~~~~
>>> 
>>> How does your compiler handles this?
>>> 
>>>   #include <iostream>
>>>   #include <complex>
>>>   #include <typeinfo>
>>> 
>>>   int main()
>>>   {
>>>     std::cout << typeid (std::conj (double (5.0))).name() << std::endl;
>>>   }
>>> 
>>> If you get back a complex number, the issue is discussed on DR 1137 [1].
>>> You should get back d for double.  I only found this DR number because
>>> it's refered on the GCC implementation of conj.
>>> 
>>> Carnë
>>> 
>>> [1] https://lwg.github.io/issues/lwg-defects.html#1137
>> 
>> I’m out of my element … I placed those lines in foo.cc and compiled using 
>> Apple’s clang
> 
> This is what I get:
> 
>    $ cat foo.cc
>    #include <iostream>
>    #include <complex>
>    #include <typeinfo>
>    int main()
>    {
>      std::cout << typeid (std::conj (double (5.0))).name() << std::endl;
>    }
>    $ g++ --std=c++11 foo.cc -o foo
>    $ ./foo
>    d
> 
>> On 11 August 2016 at 02:07, Mike Miller <address@hidden> wrote:
>> [...]
>> I took the liberty of testing with clang 3.8 on Debian.
>> 
>> With clang and llvm libc++, I get similar errors about streams and 
>> char_traits.
>> 
>> With clang and gcc libstdc++, I get the following:
>> 
>>  address@hidden:~/src$ clang-3.8 -o foo foo.cc
>>  foo.cc:7:24: error: no matching function for call to 'conj'
>>    std::cout << typeid (std::conj (double (5.0))).name() << std::endl;
>>                         ^~~~~~~~~
>>  
>> /usr/bin/../lib/gcc/x86_64-linux-gnu/6.1.1/../../../../include/c++/6.1.1/complex:677:5:
>>  note: candidate template ignored: could not match 
>> 'complex<type-parameter-0-0>' against 'double'
>>      conj(const complex<_Tp>& __z)
>>      ^
>>  1 error generated.
> 
> I think this is the issue and it should be resolving to something like this
> 
>  
> https://github.com/gcc-mirror/gcc/blob/master/libstdc%2B%2B-v3/include/std/complex#L1930
> 
> I will guess that replacing std::conj with octave::numeric::conj will also
> trigger this issue.  Octave's conj() is now just imported from std [2].
> If my guess is right, then I guess this means that octave::numeric::conj
> is never used in Octave for real types.
> 
> Carnë
> 
> [2] 
> http://hg.savannah.gnu.org/hgweb/octave/file/e43d83253e28/liboctave/numeric/lo-mappers.h#l64

I assume this traced back to changeset 9c3a3d252e80?

Ben