Add an index to an index set.

Sequence number of the index within the set, -1 in case of an error.

The following defines an index set with space for 100 entries, adds an index to the set and then retrieves its sequence number.

XPRBprob prob;
XPRBidxset iset;
int val;
   ...
iset = XPRBnewidxset(prob, "Set", 100);
val = XPRBaddidxel(iset, "first");

This function adds an index entry to a previously defined index set. The new element is only added to the set if no identical index already exists. Both in the case of a new index entry and an existing one, the function returns the sequence number of the index in the index set. Note that, according to the usual C convention, the numbering of index elements starts with 0.

XPRBgetidxel, XPRBnewidxset.