Re: for

[Paul Haahr <haahr@mv.us.adobe.com>]

> Sounds like es needs macros.  Scheme has some good ideas on that score.

yes & yes.  byron and i have been looking very hard at kent dybvig's  
extend-syntax (or whatever the hygenic version is called) system for scheme  
as a branching off point for es.

the central issue that distinguished what we want from current scheme state  
of the art is that the macro systems from lisp derived language almost alway  
want to work off atoms that appear in head position, where we're dealing  
with some infix, some prefix, and some postfix forms.

what we're going to need are some rules that allow us to say

	syntax a "|" b -> %pipe {a} 1 0 {b}
	syntax cmd "&" -> %background {cmd}
	syntax "for" "(" var "=" values ";" ... ")" body ->
		let (var = ; ...)
			while {} {
				{
					if {~ $#values 0} {
						break
					}
					var = $values(1)
					values = $values(2 ...)
				} ...
				body
			}

but also add some precedence rules and have the grammar reconfigure itself  
on the fly.  i'd call it close to state of the art, as well as a substantial  
redesign for our current yacc-driven interpreter.

paul

ps: pardon the ad hoc syntax; i'm making things up as i go along.