On 2/16/2011 10:23 PM, Hossein Haeri wrote:
Hi Eric,
When you access a member of a class template, it causes the template to be instantiated. CanBeCalled cannot legally be instantiated with two function types. Hence the error.
Function types? Are you really speaking of types of ordinary C++ functions? If so, I have to say that, by coincidence, I had not passed any function types at all. Or, am I missing anything here?
You did. Look again: arity_caller::CanBeCalled < boost::proto::_value(boost::proto::_right), EmtnTermOrGram(boost::proto::_left) >::type What do you think _value(_right) and EmtnTermOrGram(_left) are?
Also, proto::if_ takes as it's template parameter a Transform. It should be a transform that evaluates to a compile-time Boolean.
So, this problem can simply be solved by replacing the '::type' part in my code with '()' in CanBeCalled<...>() even despite the fact that I never designed my CanBeCalled<> to be a transform?
Yes. That makes it an ObjectTransform. Check the docs for ObjectTransform and proto::make.
You can easily solve both problems by making the parameter to if_ an ObjectTransform, as follows: <snip>
Unfortunately, this didn't quite help. Despite the fact that EmtnShiftFObjGram itself does compile, GCC 4.5.1 (under MinGW32, WinXP, SP3) fails to compile all the code I like. Here are my test cases, where the line annotated with *** doesn't compile. The error message I get can be found in the PS:
I don't know, and without a complete example that I can compile, I can't help you further. And a warning: I'm completely swamped with work and am not likely to be much help in the near future. Maybe you post your code to the proto list (cross-posting) and someone can chime in there. -- Eric Niebler BoostPro Computing http://www.boostpro.com