replace-match: GNU vs XEmacs

Has anyone given any thought to fixing the replace-match incompatibility between GNU Emacs and XEmacs? The optional fifth argument is different: * GNU Emacs 20.4: The optional fifth argument SUBEXP specifies a subexpression of the match. It says to replace just that subexpression instead of the whole match. This is useful only after a regular expression search or match since only regular expressions have distinguished subexpressions. * XEmacs: When fourth argument is a string, fifth argument STRBUFFER specifies the buffer to be used for syntax-table and case-table lookup and defaults to the current buffer. (When fourth argument is not a string, the buffer that the match occurred in has automatically been remembered and you do not need to specify it. I've been trying to port diff-mode.el to XEmacs, and it's difficult, as the subexpression-replacement capability of GNU Emacs is used extensively. I could managle diff-mode.el to work, but it would require a lot of effort, and I'm wondering if we can somehow fix replace-match, instead. The best solution is would be to shift the XEmacs-specific option over once place (make it the sixth option), but I don't know how much XEmacs code would have to be changed (especially, privately-written code). An ugly, kludgy solution would be to test the type of the fifth parameter; if it's a number, treat it as a subexpression index, otherwise treat it as a buffer. However, this means that you can't specify a buffer to use for syntax and case tables if a subexpression is specified. Comments, anyone? -- Darryl Okahata darrylo(a)sr.hp.com DISCLAIMER: this message is the author's personal opinion and does not constitute the support, opinion, or policy of Hewlett-Packard, or of the little green men that have been following him all day.