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From: wje@sii.UUCP (Bill Ezell)
Newsgroups: net.lang
Subject: Re: loop indexing
Message-ID: <387@sii.UUCP>
Date: Tue, 17-Jan-84 10:51:58 EST
Article-I.D.: sii.387
Posted: Tue Jan 17 10:51:58 1984
Date-Received: Wed, 18-Jan-84 06:57:09 EST
Lines: 31

b
Avl (an applications implementation language for Unix) provides a
generator facility:

	foreach(a,b)
	{
	..
	}

which means 'for each a in b'. Since the basic datatype is a tree of trees,
foreach is very useful. Because the compiler optimizes references to 'a' to
be pointers into 'b', execution is much faster than explicit iteration.

I have found this to be very natural way to deal with sets of data; it is
surprisingly rare to actually need to know the order in which things
are manipulated.

Note that Avl has no explicit pointers; the compiler hides the fact that
'a' is a pointer. This allows the efficiency gained by pointer manipulation
without the complexity (and confusion) commonly associated with explicit
pointer datatypes. 'a' is treated specially only within the scope of the
foreach.

		-Bill Ezell
		 Software Innovations, Inc.
		 (decvax!sii!wje)
		 (ittvax!sii!wje)


PS: Incidentially, Avl isn't a 'toy' language; it is currently being used
by OEM's for real applications programming.