Hi,

for my stdext::hash_map I have to implement a operator for strictly weak
ordering of my key_values which are are i,j,k coordinates which identify cells of a dynamic cell-grid.

How can I order them? Ive tried it very hard but all attempts failed so far and
gave bad results.

Here is the codebase for the problem:

struct Coordinate
{
int i,j,k;
}

class hash_compare : public stdext::hash_compare<Coordinate>
{
public:
// hash function
size_t operator() (const Coordinate& key) const
{
// hash function proposed in [Worley 1996]
return 541*key.i + 79*key.j + 31*key.k;
}

// strictly weak ordering as requested by msdn
bool operator() (const Coordinate& lhs, const Coordinate& rhs) const
{
// HERE IS THE PROBLEM: my current method is bad, since it does not conform to the strictly weak ordering rules
return (lhs.i + lhs.j + lhs.k)<(rhs.i + rhs.j + rhs.k);
}
};

// the hashtable itsself
stdext::hash_map<Coordinate, Cell, hash_compare> gridCells;

I ask because Im afraid that such ordering of i,j,k coordinates is not possible without some additional
helper variables (gridResolutionX, gridResolutionY, gridResolutionZ) which help in mapping the coordinates
onto a linear sequence. But the usage of such helper variables would destroy the purpose of a dynamic grid
and therefore the usage of a hash_map.

Thanks in advance for your help.
dave