[Albert C. Baker III]

My office mate and I found the answer last night...

so, given my key type:

template<typename T_DataList,typename T_ColumnName,typename T_CDR>
class GenericDataContainerKey
{
  .
  .
  .
  size_t hash() { return m_datum << 3 + m_cdr.hash(); } // recursive data structure
};

the desired code snippet was:

namespace __gnu_cxx
{

  template<>
  template<typename T_DataList,typename T_ColumnName,typename T_CDR>
  struct hash<GenericDataContainerKey<T_DataList,T_ColumnName,T_CDR> >
  {
    size_t operator() (const GenericDataContainerKey<T_DataList,T_ColumnName,T_CDR> &tk) const { return tk.hash(); }
  };
};

This indicates a level of template behaviour that I was heretofore unaware, i.e.
that it is legal to nest template definitions and partial specializations.

That is what we are doing here; the outer 'template<>' is an indicator that
we want to do a partial specialization of our 'struct hash'. The inner
template<...> is a standard template definition, and the nesting of the two
allows us to specify a templated definition of the partial specialization,
as desired.