On Friday 07 September 2012 10:27:55 Alex Hagen-Zanker wrote:
On 07/09/2012 08:40, Tim Blechmann wrote:
The d_ary_heap does not compile (in VS2010) when the Comparison class contains a typedef T. The typedef takes prevalence over the template parameter T when the heap is derived from the Comparison class.
I.e. the following pattern occurs:
template<class T, class Cmp> struct heap_base : Cmp {
typedef T value_type; // value_type = Cmp::T
}
I don't know if this is a bug, a user issue, or a compiler issue. But it caused me a lot of headache when I was trying to apply Jeremiah's indirect_cmp with Boost.Heap.
hm ... this code works with gcc and with clang ... afaict, msvc does not resolve T correctly.
not sure what is the best way to work around this, as every identifier that we can use instead of T could also clash with a declaration in Cmp :/
tim
You could have a workaround like this:
template<typename T, typename U, typename Parent> struct B_args { typedef T T; typedef U U; typedef Parent Parent; };
template<typename T, typename U, typename Parent> struct B : B_args<T, U, Parent> , Parent { typedef typename B_args::T value_type; };
as a replacement for:
template<typename T, typename U, typename Parent> struct B : Parent { typedef T value_type; };
... or keep Cmp as a member, if possible. Although this would defeat EBO.