Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!mailrus!uunet!mcsun!hp4nl!charon!steven
From: steven@cwi.nl (Steven Pemberton)
Newsgroups: comp.lang.misc
Subject: Re: Arrays in languages
Message-ID: <8873@boring.cwi.nl>
Date: 7 Mar 90 16:39:00 GMT
References: <3528@tukki.jyu.fi> <14251@lambda.UUCP> <8836@boring.cwi.nl> <14255@lambda.UUCP> <8849@boring.cwi.nl> <9230@wpi.wpi.edu>
Sender: news@cwi.nl (The Daily Dross)
Reply-To: steven@valk.cwi.nl.UUCP (Steven Pemberton)
Organization: CWI, Amsterdam
Lines: 67

In article <9230@wpi.wpi.edu> jhallen@wpi.wpi.edu (Joseph H Allen) writes:

> (the nicest array language I've ever used was a version of BASIC which
> didn't have a DIM statement but which handled arrays of arbitrary
> dimension and size.  I.E., you could just say 'A(1,5,10)=7' and it
> would allocate the array for you.  You could then say 'A(1,5,10,8)=9'
> and it would make the element A(1,5,10) contain a sub-array... Is
> there any other language with this power?

Sure! ABC, recently posted to the net (but *still* not appeared on
binaries.{mac, ibm.pc} and sources.unix - what are those moderators
doing?) has the equivalent:

	- no declaration of arrays, or their sizes
	- dynamically sized
	- sparse

For instance (>>> is the ABC prompt; it's an interactive language):

	>>> PUT {} IN tel		\ initialises tel to empty
	>>> PUT 4141 IN tel["Eddy"]
	>>> PUT 4999 IN tel["Babs"]
	>>> PUT 7878 IN tel["Lambert"]

	>>> WRITE tel["Babs"]
	4999

	>>> WRITE tel			\ you can write the whole array
	{["Babs"]: 4999; ["Eddy"]: 4141; ["Lambert"]: 7878}

	>>> WRITE keys tel
	{"Babs"; "Eddy"; "Lambert"}

	>>> FOR name IN keys tel:
		WRITE name, ":", tel[name] /
	Babs: 4999
	Eddy: 4141
	Lambert: 7878

Similarly with 'multi-dimension' arrays:

	>>> PUT {} IN value
	>>> PUT 1 IN value[5, 8]
	>>> PUT 13 IN value[3, 6]
	>>> PUT -1 IN value[1, 9]

	>>> WRITE value[3, 6]
	13

	>>> WRITE value
	{[1, 9]: -1; [3, 6]: 13; [5, 8]: 1}

	>>> WRITE keys value
	{(1, 9); (3, 6); (5, 8)}

Actually the keys here are single values of type 'compound', so you
may also say things like
	>>> PUT 1, 9 IN point
	>>> WRITE value[point]
	-1
	>>> IF point1 IN keys value: WRITE value[point1]
etc.

Steven Pemberton, CWI, Amsterdam; steven@cwi.nl
"Let us go then you and I/while the night is laid out against the sky/like a
					smear of mustard on an old pork pie"
Nice poem Tom. I have ideas for changes though, why not come over? - Ezra