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Path: utzoo!yetti!oz
From: oz@yetti.UUCP
Newsgroups: comp.lang.lisp
Subject: Re: First Class Environments in Scheme?
Message-ID: <179@yetti.UUCP>
Date: Mon, 26-Oct-87 01:44:12 EST
Article-I.D.: yetti.179
Posted: Mon Oct 26 01:44:12 1987
Date-Received: Tue, 27-Oct-87 06:50:42 EST
References: <3431@sol.ARPA> <23200001@silver> <2095@watcgl.waterloo.edu>
Reply-To: oz@yetti.UUCP (Ozan Yigit)
Organization: York U. Computer Science
Lines: 44
Keywords: scheme, macros

In article <2095@watcgl.waterloo.edu> Doug Moen writes:

>...
>Has anyone done work that "solves" the macro problem?
>

	Yep. It is scheme84's "syntax extension" facility:

	"Scheme84 allows the user to declare new special forms. Such
	constructs are syntactic entities that are *expanded* during 
	compilation of code that used them. In other dialects of
	lisp and other versions of Scheme, similar constructs are
	called macros" 	
			      [Scheme84 Ref Man - Rep 153]

	I think this pattern-based extension facility is so elegant 
	that it makes ordinary lisp macro facilities look like a 
	horrendous (can you say bletcherous?) cludge.

	example: syntactic extension "and"

	(declare-syntax and ()
		[(and) true]
		[(and e) e]
		[(and e1 e2 ...) (if e1 (and e2 ...) false)])

	The ellipsis (...) is a part of the definition, and used to
	specify arbitrarily long lists.

	Intrigued ? See:

		D. Friedman, C. Haynes, E. Kohlbecker and M. Wand,
		"Scheme84 Interim Reference Manual", Indiana University
		Computer Science, Tech. Rep. 153, June 1985

		E. Kohlbecker, "Using Mkmac", Indiana University
		Computer Science, Tech. Rep. 157, May 1984

oz
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