Re: [Boost-users] [phoenix][units] make boost.phoenix play well with boost.units

On 6/4/10 10:31 AM, alfC wrote:

On Jun 3, 7:16 pm, Steven Watanabe wrote:

...

Joel de Guzman wrote:

...

When you do a*a with quantitysi::length, what is the expected return type?

quantitysi::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::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). See phoenix/operator/arithmetic.hpp for example. Regards, -- Joel de Guzman http://www.boostpro.com http://spirit.sf.net