notes

http://stackoverflow.com/questions/5849203/is-there-an-implementation-of-a-binary-search-tree-annotated-with-sub-tree-size
http://sigpipe.macromates.com/2009/08/13/maintaining-a-layout/


if node_traits doesn't have get_monoid_value

the monoid must then know how to access the stored value
or we wrap the monoid in something that knows how to get to the stored value

then the hook itself holds the value in some "well known" way? must inherit from a base that can be upcast to. the monoid wrapper then 



======================

avoid template explosion

tree_algorithms<NodeTraits> must use the same node traits regardless of what monoids are supported.

======================

MonoidNodeTraits
{
	typedef ... node_traits;
};


template <typename NodeTraits, typename MonoidNodeTraits>
tree_algoritms;

// or 

template <typename NodeTraits>
class tree_algoritms_base;

template <typename MonoidNodeTraits>
class tree_algoritms : public tree_algorithms_base<typename MonoidNodeTraits::node_traits>

template <typename NodeTraits, typename MonoidNodeTraits>

=====================

class monoid_node_traits
{
	
}



alias make='make 2>&1 | fold -sw $COLUMNS | head -n $(($LINES - 2))'