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From: joel@DECWRL.DEC.COM
Newsgroups: comp.lang.modula2
Subject: Re: Number of elements in a set
Message-ID: <8709142056.AA10394@vulcan.dec.com>
Date: Mon, 14-Sep-87 17:56:57 EDT
Article-I.D.: vulcan.8709142056.AA10394
Posted: Mon Sep 14 17:56:57 1987
Date-Received: Wed, 16-Sep-87 00:44:23 EDT
References: <8709140824.AA21380@cayuga.cs.rochester.edu>
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Pascal's set constructors are untyped, and there are cases where context iss
insufficient to determine at compile time the boundaries of a set.

Most implementations thus implement sets of some small, fixed, size (like 16,
32, 128, or 256 elements).  The UCSD implementations go to some pains to allow
dynamically sized sets up to 4096 elements (8-bit microcomputers can deal with
256 16-bit words without too much grief).

Modula-2's set constructors are typed, and therefore the size of the set is
always known at compile time.

Many implementations nonetheless implement sets as the word size of the
machine, because then it's easy to generate single machine instructions.  It
is not hard  to implement sets of effectively unbounded size; further, it is
usually more efficient, and certainly more readable and useful to have large
sets than to simulate this with the corresponding user code.

One can only hope that the eventual ISO standard will say something useful
about sets, like you can have at least as many elements as, say, MAXINT.  But
people who haven't implemented such tend to vote against inclusion of such
language, so don't count on it.

- Joel McCormack {ihnp4 decvax ucbvax allegra}!decwrl!joel
		 joel@decwrl.dec.com