From mernst@theory.lcs.mit.edu Mon Mar 14 17:30:10 EST 1994
Article: 12277 of comp.lang.lisp
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From: mernst@theory.lcs.mit.edu (Michael Ernst)
Newsgroups: comp.lang.lisp
Subject: Re: help: loading macros from a file (mit-scheme)
Date: 14 Mar 94 11:53:45
Organization: MIT Lab for Computer Science
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In-reply-to: ian@yahi.cse.ucsc.edu's message of 11 Mar 1994 20:46:56 GMT

In article <2lqlc0$dq2@darkstar.UCSC.EDU> ian@yahi.cse.ucsc.edu (ian barland) writes:
> Hi, I am using MIT-scheme (v7.3b).
> I use "define-macro" and all goes smoothly, except that
> when the macro is defined in a (.scm) file and I try to "load" the
> file, the macro is in effect only for that file,
> and isn't available back at the level where I did the "load" from
> (which is what I want).

Here is some code, written by Roger Crew, that deals with the problem of
define-macro having effect only for the current file.  Use
define-global-macro where you were using define-macro, and the macro
definition will be in effect even after the file containing it is loaded.

					-Michael Ernst
					 mernst@theory.lcs.mit.edu



;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; Macros
;;;

;;; Annoying observation about define-macro:
;;; it appears that (load ...) pushes a syntax table that gets
;;; popped upon EOF.  Thus we seem to need a means of exporting
;;; macro definitions to other files...

;; 
;; define-system-global-macro
;;   defines a macro that, for whatever reason, must live alongside 'if
;;   and 'lambda.
;; 
;; define-global-macro
;;   defines a macro that is global to the zaphod world (i.e., wherever you
;;   were using define-user-macro before).  This currently is identical to
;;   define-user-macro, but will eventually change.
;; 
;; define-user-macro
;;   defines a macro that is strictly for the user's playground, e.g.,
;;   abbreviations for test suites.  Most of the time it will suffice to
;;   type (define-macro...) to the prompt, but it may be convenient to
;;   have a collection of useful user macros in a file, in which case
;;   you'll need define-user-macro.
;; 

(syntax-table-define
    system-global-syntax-table
    'define-system-global-macro
  (macro (template . body)
    `(syntax-table-define
	 system-global-syntax-table
	 ',(car template)
       (macro ,(cdr template)
	 ,@body))))

(syntax-table-define
    system-global-syntax-table
    'define-global-macro
  (macro (template . body)
    `(syntax-table-define
	 user-initial-syntax-table
	 ',(car template)
       (macro ,(cdr template)
	 ,@body))))

;; For now, make define-user-macro identical to define-global-macro
(define-system-global-macro (define-user-macro . def)
  `(define-global-macro ,@def))


(set! sf/default-syntax-table user-initial-syntax-table)
;; This is necessary so that the compiler knows about global macros
;; I don't like this, but it'll do for now.
;; For a stomach-churning alternative, see syntax.scm  --RFC 6/8/93