[ConceptGCC]|
[ConceptGCC] |
ConceptGCC :Re: Requiring a function template specialization |
From: Tom Honermann (tom.honermann_at_[hidden])
Date: 2007-06-06 19:39:07
Hi Walter,
My apologies, it seems as though I have been living under a rock. I was
under the impression that function template specializations did not
exist. My reference to non-partial specializations was a mis-nomer - I
was trying to glaze over the fact that function overloads can look
similar to template partial-specializations even though they aren't. I
should have been more precise.
I tried a few other syntaxes I thought might work and was able to
reproduce the ICE on Linux (conceptgcc-boostcon), but I couldn't find a
way to work around the ICE.
Tom.
Walter E Brown wrote:
>Thank you for the reply. Unfortunately, your assumptions as to what I
>intended are not correct: I really did intend a niladic (0-argument)
>foo function, so I agree with you that overloading won't suffice.
>
>I don't know what you mean by "C++ does not support function template
>non-partial specializations." If a specialization is "non-partial", it
>must be a complete specialization, and C++03 certainly does support
>complete specializations for function templates. If you meant that
>"C++03 does not support function template partial specializations," then
>I agree with you, but there is no partial specialization anywhere in my
>example below.
>
>I really do want the Foo<T> concept to require the existence of a
>foo<T>() function template specialization. Because conceptgcc today
>breaks (ICE) on my proposed code, I simply want to know whether that
>syntax will be correct once conceptgcc is fixed. If not, what is the
>correct way to specify my requirement?
>
>And if the requirement can't be specified today, then I will argue that
>we need to modify the Concepts proposal until the requirement can be
>specified. I firmly believe that Concepts must be capable of specifying
>an arbitrary legal C++ interface.
>
>Thanks again for writing. Best,
>
>-- WEB
>
>
>On 2007-06-06 4:25 PM, Tom Honermann wrote:
>
>
>>Hi Walter,
>>
>>C++ does not support function template non-partial specializations.
>>Function overloading provides this capability without the need for
>>specialization (non-template functions are searched for a match before
>>template functions). Correct me if I am wrong, but the goal of your
>>concept is just to ensure that there is a function 'foo' that can be
>>called with a parameter of type 'T', yes? If so, you don't need to
>>specify templating at all. Something like this should work:
>>
>> concept Foo< class T >
>> {
>> // Require a function 'foo' that accepts an rvalue
>> // of type T and returns an rvalue of type T
>> T foo(T);
>> };
>>
>>In your example, 'foo' does not accept any arguments. In this case, function overloading is not possible, but you could still require that there is a function named 'foo' that accepts no parameters and returns type T. I'm assuming you just omitted the arguments in your example.
>>
>>Tom.
>>
>>
>>Walter E Brown wrote:
>>
>>
>>>I would like to express a concept, Foo<T>, that requires the existence
>>>of a specialization, foo<T>, of a function template.
>>>
>>>I tried the following with conceptgcc-boostcon under Cygwin, but got an
>>>ICE (I submitted a bug report earlier today):
>>>
>>> #include <concepts>
>>>
>>> concept Foo< class T >
>>> {
>>> template<>
>>> T
>>> foo<T>();
>>> };
>>>
>>>Is the above the correct way to express the desired concept? Thanks,
>>>
>>>-- WEB
>>>_______________________________________________
>>>ConceptGCC mailing list
>>>ConceptGCC_at_[hidden]
>>>http://www.osl.iu.edu/mailman/listinfo.cgi/conceptgcc
>>>
>>>
>>>
>>--
>>Oracle Email Signature Logo
>>Tom Honermann | Senior Principal Software Engineer | 503.276.2354
>>Oracle PeopleTools Development
>>1211 SW 5th Ave, Suite 9080, Portland, OR 97204
>>
>>
>>------------------------------------------------------------------------
>>
>>_______________________________________________
>>ConceptGCC mailing list
>>ConceptGCC_at_[hidden]
>>http://www.osl.iu.edu/mailman/listinfo.cgi/conceptgcc
>>
>>
>_______________________________________________
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>ConceptGCC_at_[hidden]
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>
>
-- Oracle Email Signature Logo Tom Honermann | Senior Principal Software Engineer | 503.276.2354 Oracle PeopleTools Development 1211 SW 5th Ave, Suite 9080, Portland, OR 97204
