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
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 \
{ \
typedef \
- typename proto::detail::uncvref<A0>::type \
+ decltype( name(typename
proto::detail::uncvref<A0>::type()) ) \
type; \
}; \
template \
- 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
