Re: [boost] Unittest capability for meta-programs feedback request

Subject: Re: [boost] Unittest capability for meta-programs feedback request
From: Steven Watanabe (watanabesj_at_[hidden])
Date: 2011-09-28 10:22:17

AMDG

On 09/27/2011 11:06 PM, Ben Robinson wrote:
> The required modification to Boost Unit, was to add the following templated
> constructor to boost::units::quantity:
> 
>         template <class rhs_type>
>         quantity(const rhs_type& source) : val_()
>         {
>             BOOST_METATEST_MSG(false,
> INVALID_CONVERSION_BETWEEN_INCOMPATIBLE_UNITS, (this_type, rhs_type));
>         }
> 
> In the unmodified library, the lack of this constructor would produce the
> compiler error, when an incorrect assignment requiring this constructor was
> made.  This makes an interesting point, that I have written additional code
> to *explicitly* express the intended failure consequence of invoking this
> constructor, instead of relying *implicitly *on the lack of such a
> definition.
> 

Unfortunately, this changes the behavior of
the library.  is_convertible<Q1, Q2> will return
true if the units are unrelated.  It can also
change the result of overload resolution.

In Christ,
Steven Watanabe