[Development] How to make a fancy QMap c++17 initializer_list

[Grégoire Barbier]

Le 24/07/2017 à 21:44, Henry Skoglund a écrit :
> On 2017-07-24 21:32, Grégoire Barbier wrote:
>> Le 24/07/2017 à 18:45, Henry Skoglund a écrit :
>>>      QMap m1 = {std::pair{2,"score"}, {4,"seven"}, {1,"Four"}, 
>>> {5,"years"}, {3,"and"}, {6,"ago"}};
>>
>> Or even this:
>>
>> QMap<int, const char*> m1 { {2, "score"}, {4, "seven"}, };
>>
> 
> Yes that works nicely too but it's not bleeding edge/c++17 :-)
> 
> This post was just to show that in c++17 it's possible to declare a QMap 
> without any trailing <> i.e. letting the compiler figure out the types 
> (less visual clutter) More here: 
> http://en.cppreference.com/w/cpp/language/class_template_argument_deduction
> 
> Rgrds Henry

Sorry I missed your point, by far.

Anyway it's not easy: I played a little bit on godbolt.org and locally 
on my computer and it seems that gcc 7.1 only deduces templates argument 
with a depth of 1 (never with templates of templates), ICC 17 and MSVC 
15.2 being worst on this point (not deducing at all, if I did not miss 
something).

Even when addind deduction guides like I tried here: 
https://godbolt.org/g/pC8SaV

So, I'll wait and keep my explicit template arguments if needed a few 
more years, and keep being thankful to all pioneers like you who use it 
now and will make compilers better... :-)

-- 
Grégoire Barbier :: g à g76r.eu