On 6/4/10 10:31 AM, alfC wrote:
On Jun 3, 7:16 pm, Steven Watanabe<watanab...@gmail.com> wrote:
Joel de Guzman wrote:
When you do a*a with quantity<si::length>, what is the expected return type?
quantity<si::area> rigth.
and in case you wonder, Boost.Units has a bunch of template functions to obtain the result type of arithmetic operations. For example boost::units::multiply_typeof_helper<X,Y>::type, these are heavily used in boost/units/lambda.hpp, which makes lambda play well with units.
(looks like a phoenix-2 limitation. hopefully, this will all get sorted out with phoenix-3).
so, there is no hope with phoenix-2? can't we do something temporary like boost/units/lambda.hpp to help phoenix-2 to deduce the type? is it possible?
There is hope. Just specialize boost::phoenix::result_of_xxx (e.g. boost::phoenix::result_of_plus<X, Y>). See phoenix/operator/arithmetic.hpp for example. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net