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From: ldo@waikato.ac.nz (Lawrence D'Oliveiro, Waikato University)
Newsgroups: comp.lang.misc
Subject: Re: Closures (was Re: class-sic.)
Message-ID: <1991Jan21.120628.2749@waikato.ac.nz>
Date: 20 Jan 91 23:06:28 GMT
References: <20058@yunexus.YorkU.CA> <27942:Jan902:20:0791@kramden.acf.nyu.edu> <27770.278aef90@kuhub.cc.ukans.edu> <22345:Jan1021:30:4591@ <KERS.91Jan11090533@cdollin.hpl.hp.com>
Organization: University of Waikato, Hamilton, New Zealand
Lines: 23

kers@hplb.hpl.hp.com (Chris Dollin)'s comments in
KERS.91Jan11090533@cdollin.hpl.hp.com> on closures and the lambda-calculus
really bring back some memories from my earliest readings in computer science.

Is there anybody else left in the world who thinks closures are
a pretty neat idea, and a damned (pardon my French) useful programming
technique?

The only surviving language I know of that implements a proper
closure facility is POP-11. Some LISP hackers seem to think they've got
closures too, but they haven't--all they've got is an almost-as-useful
kludge that requires call frames to be allocated on the heap.

These days, I do most of my programming in von-Neumann-like languages
like Modula-2. Even here it's possible to implement closures, by
stepping outside the language slightly. It involves knowing the
machine-specific conventions for passing arguments. It also helps
if your compiler lets you insert machine code in-line.

Lawrence D'Oliveiro                       fone: +64-71-562-889
Computer Services Dept                     fax: +64-71-384-066
University of Waikato            electric mail: ldo@waikato.ac.nz
Hamilton, New Zealand    37^ 47' 26" S, 175^ 19' 7" E, GMT+13:00