Re: [boost] [Units] A first step to ease the usage of Units' quantities inside of functors created with the Lambda library

From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2008-05-28 12:08:14

AMDG

Torsten Mähne wrote:
> I noticed that currently Units and Lambda use two independent systems of
> trait classes to determine the return type of algebraic operations like
> +, -, *, /.

Boost.Units actually relies on Boost.Typeof for user types.

> - Can some of the partial specializations be dropped?
>   

I don't think so.

> - Is there a need to add other specializations
>   (e.g, for boost::units::unit<Dim, System, Enable>)?
>   

Drop the Enable parameter, it's an implementation detail which I plan to 
remove soon.

> - Is there a way to work around boost::lambda:bind's limitation
>   concerning the binding of overloaded functions? The required
>   static_cast to the function pointer (referring, e.g., a function
>   from boost/units/cmath.hpp) is tedious.
>   

The problem is avoided by creating a function object.  (untested)

struct sin_t {
    template<class Args>
    struct sig {
        typedef typename boost::tuples::element<0>::type arg1_type;
        BOOST_TYPEOF_NESTED_TYPEDEF(nested, (sin(make<arg1_type>())));
        typedef typename nested::type type;
    };
    template<class T>
    ... operator()(const T& arg) { return(sin(arg)); }
};

In Christ,
Steven Watanabe