What does the argument list in C-h f delete-duplicates mean?

Hello, XEmacs. When I do C-h f delete-duplicates, the resulting text starts off: `delete-duplicates' is a built-in function -- loaded from "/home/acm/emacs/xemacs.hg/xemacs/src/sequence.c" (delete-duplicates SEQUENCE &key (TEST #'eql) (KEY #'identity) (START 0) END FROM-END TEST-NOT) . What does this mean? In particular, I have never seen parenthesised expressions, such as "(TEST #'eql)" inside an argument list before. The XEmacs manual (page "Name Help") doesn't explain this. Are TEST, KEY and START some sort of optional parameters, or what? Thanks for the elucidation! -- Alan Mackenzie (Nuremberg, Germany). _______________________________________________ XEmacs-Beta mailing list XEmacs-Beta(a)xemacs.org http://lists.xemacs.org/mailman/listinfo/xemacs-beta