I have the following problem using a multi index container which is uniquely ordered on a pair <int,int>.
Each time i want to find every pair i that contains a specific integer. The other value of the pair is irrelevant.

An example:
<0,1>
<0,2>
<0,3>
<1,2>
<1,3>
<2,3>

and I want to find all the pairs with the value 0 as the first integer.
function find() wants the whole pair
and iterator find(const CompatibleKey& x,const CompatibleCompare& comp)const; doesn't help ,too.

Here is the declaration of my container

typedef pair<int, int> clusterset;
struct cluster {
    clusterset pair;
    float distance;
    cluster(clusterset pair, float distance) :
        pair(pair), distance(distance) {}
};

struct cluster_pair{};
struct cluster_distance{};

typedef multi_index_container<
    cluster,
    indexed_by<
        ordered_unique<
            tag<cluster_pair>, BOOST_MULTI_INDEX_MEMBER(cluster, clusterset, pair)>,
        ordered_non_unique<
            tag<cluster_distance>, BOOST_MULTI_INDEX_MEMBER(cluster, float, distance)> >
> cluster_index;

Any ideas?