add functions `stable-union' and `stable-intersection' to do stable set operations -------------------- ChangeLog entries follow: -------------------- lisp/ChangeLog addition: 2010-02-22 Ben Wing <ben@xemacs.org> * cl-seq.el: * cl-seq.el (stable-union): New. * cl-seq.el (stable-intersection): New. New functions to do stable set operations, i.e. preserve the order of the elements in the argument lists, and prefer LIST1 over LIST2 when ordering the combined result. The result looks as much like LIST1 as possible, followed (in the case of `stable-union') by any necessary elements from LIST2, in order. This is contrary to `union' and `intersection', which are not required to be order- preserving and are not -- they prefer LIST2 and output results in backwards order.