Hello, I am working on VexCL (https://github.com/ddemidov/vexcl) - a vector expression template library for OpenCL. I have recently added support for automatic generation of OpenCL kernels from generic functors (description of the feature: https://github.com/ddemidov/vexcl#function-generator). In order to implement this, I pass the instances of vex::symbolic<T> class to the given functor. vex::symbolic<T> dumps to output stream any arithmetic operations it is being subjected to, and that's how I am able to construct the OpenCL kernel source. The symbolic<T> class is of course a Boost.Proto terminal. Now, it seems natural to use Boost.Phoenix to provide the generic functors for the function generator. And indeed it is possible with simple expressions (see https://github.com/ddemidov/vexcl/blob/a95dfdd68/tests/generator.cpp#L124). However, if I try to bring cmath functions overloads from <boost/phoenix/stl/cmath.hpp> and use those ( https://github.com/ddemidov/vexcl/commit/b95da14e51), I get compilation errors. The reason apparently is that boost::phoenix_impl::<function>_impl assumes that result of <function>(expr) has the same type as expr itself. This of course is not true if expr is a Boost.Proto expression. Everything works as intended with the following patch: --- a/cmath.hpp +++ b/cmath.hpp @@ -25,11 +25,11 @@ namespace boost { struct result<This(BOOST_PHOENIX_A(n))> \ { \ typedef \ - typename proto::detail::uncvref<A0>::type \ + decltype( name(typename proto::detail::uncvref<A0>::type()) ) \ type; \ }; \ template<BOOST_PHOENIX_typename_A(n)> \ - A0 operator()(BOOST_PHOENIX_A_const_ref_a(n)) const { \ + auto operator()(BOOST_PHOENIX_A_const_ref_a(n)) const -> decltype( name(BOOST_PHOENIX_a(n)) ) { \ using namespace std; \ return name(BOOST_PHOENIX_a(n)); \ } \ I understand this is unacceptable in its current form (because it uses c++11 features), but I could not do this in terms of e.g. boost::result_of. May be someone has a better idea of how to implement this? -- Best regards, Denis