inedgegroup

int  inedgegroup(string filename, string groupname, int pointnum0, int pointnum1)

int  inedgegroup(int input, string groupname, int pointnum0, int pointnum1)

Returns 1 if the edge specified by the point pair is in the group specified by the string. This function returns 0 if the group does not exist or if the edge is not contained in the group.

This can use ad-hoc groups, like p29-30. It matches the SOP group naming convention, in particular that an empty string means all edges.