Re: [boost] [Concepts] Definition. Was [GSoC] [Boost.Hana] Formal review request

Subject: Re: [boost] [Concepts] Definition. Was [GSoC] [Boost.Hana] Formal review request
From: Mostafa (mostafa_working_away_at_[hidden])
Date: 2014-08-05 06:14:13

On Tue, 05 Aug 2014 01:59:34 -0700, Roland Bock <rbock_at_[hidden]> wrote:

> On 2014-08-05 10:30, Krzysztof Czainski wrote:
>> 2014-08-05 6:33 GMT+02:00 Michael Shepanski <mps_at_[hidden]>:
>>
>>> On 5/08/2014 1:39 AM, Roland Bock wrote:
>>>
>>>> On 2014-08-04 13:32, Mostafa wrote:
>>>>
>>>>> Concepts are sets of types
>>>>>
>>>> I think you are mistaken. A concept is a set of requirements,
>>>>
>>> I am under a New Year's resolution not to start philosophical  
>>> arguments,
>>> but this one has already begun, so ...
>>>
>> Please don't forget, that not all requirements can be checked at compile
>> time. For example: TotallyOrdered. Just by checking, that an expression
>> (a<b) is valid and yields something boolable, you can't distinguish  
>> between
>> TotallyOrdered, PartiallyOrdered, or maybe neiter.
>>
>> So, while I think it doesn't matter, whether we view concepts as sets of
>> types or requirements
> Well, if you consider TotallyOrdered a concept, then by this reasoning,
> it cannot be a set of types. But it could be a set of requirements :-)

Yes it can. TotallyOrdered := { T | if a,b,c are objects of T then ... }