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From: norskog@fortune.UUCP (Lance Norskog)
Newsgroups: net.lang
Subject: Re: loop indexing - (nf)
Message-ID: <2287@fortune.UUCP>
Date: Mon, 16-Jan-84 15:18:33 EST
Article-I.D.: fortune.2287
Posted: Mon Jan 16 15:18:33 1984
Date-Received: Wed, 18-Jan-84 01:15:14 EST
References: <2283@fortune.UUCP>
Organization: Fortune Systems, Redwood City, CA
Lines: 32

A more generalized form of this is:

	for x,y in sequence(x,y) 
		Fragment
	rof

	.
	.
	.


	GENERATOR sequence(a:int,b:boolean)
		loop
			.
			.
			yield a,b
			.
			.
		pool
	ROTARENEG

Every 'yield' is implemented as a procedure call: Fragment(a,b).
When 'sequence' returns, the for loop is over.

The only place I have seen this is in academic "toy" languages;
the only implemented version I have used was the language
"Small" in a compiler class; we had to add features
to a skeletal language and its parser/compiler/interpreter
system.  I thought generators (we called them "iterators")
were cute so I implemented them as my project.  
They are a halfway step to object-oriented programming in a procedural language.