Re: [Boost-users] [Range] Extending the library for a base class and all its derived - enable_if

On 04/26/2014 07:05 AM, Nathan Ridge wrote:

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Would something like

template <typename C> struct range_iterator, C>::type> { ... };

work? This does not compile.

Well, it should be

template <typename C> struct range_iterator::value, C>::type> { ... };

but an simpler example I tried also does not compile, complaining that template parameter C is not used (though it clearly is). I wonder if it's a bug in the error message (and the code is disallowed) or a real compiler bug. The code is disallowed. In order to select the partial specialization for some argument type 'A', the compiler would have to compare 'A' and 'typename enable_if::value, C>::type' and deduce 'C'. It cannot do this (in standardese this is called a "non-deduced context").

Ok, thanks for the clarification.