Your email inspired me to go look through code as I was certain I had run into this too. Turns out I have similar code to below with a comment that says" todo figure out why this needs to be indirected". If it is any help, I had this problem on BOTH GCC4 and VC71, so it doesn't seem to be a compiler specific issue. On 11/1/05 11:21 AM, "Eric Niebler" <eric@boost-consulting.com> wrote:
I have an MPL sequence of metafunction classes. I want to apply<> each with mpl::transform. So I did this:
struct metafnclass { template<typename T> struct apply { typedef T type; }; };
typedef mpl::vector<metafnclass, metafnclass> metafnclasses;
typedef mpl::transform< metafnclasses , mpl::apply<mpl::_1, int>
::type transmetafnclasses;
This fails horribly, and I don't know why. If I add an indirection like this:
template<typename T,typename U> struct indirect_apply : mpl::apply<T, U> {};
typedef mpl::transform< metafnclasses , indirect_apply<mpl::_1, int>
::type transmetafnclasses;
then it works fine. Why should that be? Is something getting evaluated too eagerly?