
Boost Users : 
From: Ovanes Markarian (om_boost_at_[hidden])
Date: 20070619 10:21:34
[...]
> Thanks, iterator_range works fine. What's not very nice to me is the T typename is lost for empty
>sequence and after using a metafunction, so vector_c is not really usable for metaprograming, its
>just a macro to easier define a vector.
Well... Type never gets lost in C++ ;)
What about:
typedef mpl::vector_c<float, 2.0,2.1,2.2> my_vector;
BOOST_MPL_ASSERT(( is_same< mpl::front<my_vector>::type::value_type, float > ));
vector_c initializes a vector with integral_c derived type (like mpl::int_ or mpl::bool_) and
value specified, so in this example we have most probably an mpl::vector of integral_c<float,
2.0>,..., integral_c<float, 2.2>.
Anyway applying a front metafunction to any element of vector will return some integral_c<float,
X> specification. Since you are interested in type contained in integral_c you can access it via
integral_c<float, X>::value_type. Therefore:
mpl::front<my_vector>::type::value_type
^^^^ ^^^^^ + => integral_c<float, X>::value_type
+ => integral_c<float, X>
result in correct type resolution stored in mpl::vector.
Hope that helps.
With Kind Regards,
Ovanes Markarian
Boostusers list run by williamkempf at hotmail.com, kalb at libertysoft.com, bjorn.karlsson at readsoft.com, gregod at cs.rpi.edu, wekempf at cox.net