c++ recursive mpl::equal problem?

boost, boost-mpl, c++, templates

Solution

`mpl::transform` doesn't create `mpl::vector<>`'s in your case but `mpl::vector2<>`'s. These are different types, even if they are semantically equivalent. So if you write:

typedef mpl::vector2< 
    mpl::vector2<int, char>, mpl::vector2<char, char> 
> type_1;

typedef mpl::transform< 
    mpl::vector<mpl::vector<int>, mpl::vector<char> >
  , mpl::push_back<mpl::_, char> 
>::type type_2; 

BOOST_MPL_ASSERT(( mpl::equal<type_1, type_2> ));

the assert will not fire.

Problem

i need an mpl::equal like procedure that supports recursion on types. ``` namespace mpl = boost::mpl; BOOST_MPL_ASSERT(( mpl::equal< mpl::vector<int, char>, typename mpl::push_back<mpl::vector<int>, char>::type > )); // OK ``` the above compiles fine, however if i use it in mpl::transform or mpl::fold, visual studio 2010 rc1 complains. ``` typedef mpl::vector< mpl::vector<int, char>, mpl::vector<char, char>> type_1; typedef mpl::transform< mpl::vector< mpl::vector<int>, mpl::vector<char>>, mpl::push_back<mpl::_, char>>::type type_2; BOOST_MPL_ASSERT(( mpl::equal<type_1, type_2> )); // FAILS ``` however, these work... ``` BOOST_MPL_ASSERT(( mpl::equal< typename mpl::at_c<type_1, 0>::type, typename mpl::at_c<type_2, 0>::type> )); // OK BOOST_MPL_ASSERT(( mpl::equal< typename mpl::at_c<type_1, 1>::type, typename mpl::at_c<type_2, 1>::type> )); // OK ``` is it that mpl::equal does not work on dynamically generated recursive types, or is there something wrong with my syntax? any advice would greatly appreciated.

Original source