// * Create: allocates an initialises the OSet. Arguments:
// - keyOff The offset of the key within the element.
-// - elemSize The size of the element.
// - cmp The comparison function between keys and elements, or NULL
// if the OSet should use fast comparisons.
// - alloc The allocation function used for allocating the OSet itself;
/*--- Operations on OSets ---*/
/*--------------------------------------------------------------------*/
+// In everything that follows, the parameter 'key' is always the *address*
+// of the key, and 'elem' is *address* of the elem, as are the return values
+// of the functions that return elems.
+//
// * Size: The number of elements in the set.
//
// * Contains: Determines if any element in the OSet matches the key.