# HG changeset patch
# User Aidan Kehoe <kehoea@parhasard.net>
# Date 1233751274 0
# Node ID 0347879667ed19a6c266459147ca271d05581238
# Parent  8891b0477058c16e7c74700cb279cba0ad8fcb39
Document the force-coding-system-equivalency macro in coding.el.

lisp/ChangeLog addition:

2009-02-04  Aidan Kehoe  <kehoea@parhasard.net>

	* coding.el (force-coding-system-equivalency):
	Document this macro and the motivation for it.

diff -r 8891b0477058 -r 0347879667ed lisp/ChangeLog
--- a/lisp/ChangeLog	Wed Feb 04 12:35:45 2009 +0000
+++ b/lisp/ChangeLog	Wed Feb 04 12:41:14 2009 +0000
@@ -1,3 +1,8 @@
+2009-02-04  Aidan Kehoe  <kehoea@parhasard.net>
+
+	* coding.el (force-coding-system-equivalency): 
+	Document this macro and the motivation for it. 
+
 2009-01-15  Aidan Kehoe  <kehoea@parhasard.net>
 
 	* coding.el (force-coding-system-equivalency):
diff -r 8891b0477058 -r 0347879667ed lisp/coding.el
--- a/lisp/coding.el	Wed Feb 04 12:35:45 2009 +0000
+++ b/lisp/coding.el	Wed Feb 04 12:41:14 2009 +0000
@@ -246,6 +246,14 @@
 ;;; Make certain variables equivalent to coding-system aliases:
 (macrolet
     ((force-coding-system-equivalency (&rest details-list)
+       "Certain coding-system aliases should correspond to certain variables.
+
+This macro implements that correspondence. This gives us compatiblity with
+other Mule implementations (which don't use the coding system aliases), and
+a certain amount of freedom of implementation for XEmacs; using a variable's
+value in C for every file operation or write to a terminal in C is probably
+an improvement on the hash-table lookup(s) necessary for a coding system
+alias, though we haven't profiled this yet to see if it makes a difference."
        (loop for (alias variable-symbol)
          in details-list
          with result = (list 'progn)