To make a struct a valid key type, do I need to implement both opCmp and opEquals or just one or the other? It says on the page about associative arrays: "The implementation may use either opEquals or opCmp or both." Does that mean it uses whichever one is user-defined (or both if they're both user-defined)? Or does it mean the user is responsible for defining both?
Immediately after that it says: "Care should be taken so that the results of opEquals and opCmp are consistent with each other when the struct/union objects are the same or not.", certainly this means that if a.opEquals(b), then a.opCmp(b) should be 0, but does the converse have to be true?
