function wrapper( ia, ib ) {
				var a = tuple[ indices[ ia ] ];
				var b = tuple[ indices[ ib ] ];
				return clbk( a, b );
			}
Wraps a comparison function to allow sorting the internal indices array rather than the tuple directly.

@private
@param {NonNegativeInteger} ia - first index
@param {NonNegativeInteger} ib - second index
@returns {*} value specifying the sort order