Re: [Boost-users] Please help with enable_if problem

Subject: Re: [Boost-users] Please help with enable_if problem
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2010-04-13 21:06:13

AMDG

John Dlugosz wrote:
> I'm getting tons of this from Microsoft's compiler:
>
> 	error C2893: Failed to specialize function template 'enable_if<boo...
>   

Without the actual error message, I'm not sure I can help much.

> but isn't that the whole point of using enable_if?  I'm using it already in my project and understand the idea behind it.
>
> Here is the function in question:
>
> 	template <typename T, typename D>
> 	typename enable_if<
> 	   boost::mpl::and_<
> 	      std::tr1::is_base_of<generic_linear_time_ntbase, T>, 	   
> 	      boost::mpl::or_<
> 	         is_dimensional_time<D>, 
> 	         std::tr1::is_same<duration,D>,
> 	         std::tr1::is_same<linear_duration,D> 
> 	         > 
> 	      >,
> 	   T>::type&
> 	operator+= (T& left, const D& right)
> 	 {
> 	 left.addop_ (right);  // real implementation is in the generic base class
> 	 return *this;  // but I need this template to return the correct derived (actual) class.
> 	 }
>   

This can't be the real code, because it wouldn't compile
as a member because it takes two arguments, and wouldn't
compile as a non-member, because it uses "this."

In Christ,
Steven Watanabe