Re: [boost] [config] What Feature is this??

Subject: Re: [boost] [config] What Feature is this??
From: Edward Diener (eldiener_at_[hidden])
Date: 2017-07-24 15:18:59

On 7/24/2017 8:29 AM, Andrey Semashev via Boost wrote:
> On 07/24/17 14:37, Edward Diener via Boost wrote:
>> On 7/23/2017 2:50 PM, John Maddock via Boost wrote:
>>> Folks, I think I'm looking to add a new C++11 defect macro, but don't 
>>> know what the feature is called, nor can I see a way of detecting it 
>>> with clang's __has_feature function.
>>>
>>> The code I want to enable involves function overloading based on a 
>>> decltype return type as in:
>>
>> I never realized that function overloading could occur based on any 
>> return type. I always thought it had to be based on the parameter 
>> types. Is this part of the C+11 standard ? Where in the standard is 
>> this specified ?
> 
> I think it's not about overloading but about disabling function template 
> instantiations via SFINAE.

I am glad to hear that. I misinterpreted the original message and 
probably should have realized it. Thanks !

> 
>>> auto integrate(args...) -> decltype(expression1);
>>>
>>> auto integrate(args...) -> decltype(expression2);
>>>
>>>
>>> where expression1 and expression2 are two mutually exclusive options 
>>> (the conceptual requirements of args means that only one of these 2 
>>> will ever be satisfied).
>>>
>>> This works fine in msvc-14 and later and gcc-4.8 and later, but I 
>>> don't see any current config macros which cover this case, nor can I 
>>> figure out what this trick should be called.
>>>
>>> Alternatively, if anyone has a better way of differentiating between 
>>> unary and binary functions I'm happy to hear about it ;)
>>>
>>>
>>> Thanks, John.
>>>
>>>
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