CMUCL commit: RELEASE-20B-BRANCH src/code (extfmts.lisp)

[Raymond Toy]

    Date: Monday, September 6, 2010 @ 11:35:29
  Author: rtoy
    Path: /project/cmucl/cvsroot/src/code
     Tag: RELEASE-20B-BRANCH

Modified: extfmts.lisp

code/extfmts.lisp
o Add some comments from Paul Foley on what arguments to DEF-EF-MACRO
  mean.


--------------+
 extfmts.lisp |   24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)


Index: src/code/extfmts.lisp
diff -u src/code/extfmts.lisp:1.35.4.5 src/code/extfmts.lisp:1.35.4.6
--- src/code/extfmts.lisp:1.35.4.5	Sun Sep  5 21:01:27 2010
+++ src/code/extfmts.lisp	Mon Sep  6 11:35:28 2010
@@ -5,7 +5,7 @@
 ;;; domain.
 ;;; 
 (ext:file-comment
- "$Header: /project/cmucl/cvsroot/src/code/extfmts.lisp,v 1.35.4.5 2010-09-06 01:01:27 rtoy Exp $")
+ "$Header: /project/cmucl/cvsroot/src/code/extfmts.lisp,v 1.35.4.6 2010-09-06 15:35:28 rtoy Exp $")
 ;;;
 ;;; **********************************************************************
 ;;;
@@ -697,7 +697,27 @@
 
 ;;; DEF-EF-MACRO  -- Public
 ;;;
-;;; 
+;;; Create an ef-macro (external-format macro).  This creates a
+;;; function named Name that will process an external format in the
+;;; desired way.
+;;;
+;;; Paul Foley says:
+;;;   All the existing ef-macros are provided with the implementation,
+;;;   so they all use lisp::lisp as the id; it's intended for people
+;;;   who want to write their own macros~there are some number of
+;;;   slots (+ef-max+) used by the implementation; the idea is that
+;;;   you can write something like (def-ef-macro foo (ef my-tag 4 1)
+;;;   ...) to implement 1 of a total of 4 new macros in your own
+;;;   "namespace", without having to know how many are implemented by
+;;;   others (e.g., the 10 used by the base implementation...which
+;;;   could change with the next release -- and if several libraries
+;;;   each add their own, the total number, and the position of each
+;;;   one's slots within that total, may change depending on load
+;;;   order, etc.)  When you write the above, it allocates 4 new
+;;;   places and associates the base index with "my-tag", then the
+;;;   "idx" value is relative to that base.  The id lisp:lisp always
+;;;   has its base at 0, so it doesn't need to go through ensure-cache
+;;;   to find that out.
 (defmacro def-ef-macro (name (ef id reqd idx) body)
   (let* ((tmp1 (gensym))
 	 (tmp2 (gensym))