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From: Mark H Weaver <mhw@netris.org>
To: Stefan Israelsson Tampe <stefan.itampe@gmail.com>
Cc: guile-devel@gnu.org
Subject: Re: a rehash of the question of optimizing some prompt ideoms
Date: Sat, 31 Aug 2013 00:35:20 -0400	[thread overview]
Message-ID: <87k3j232bb.fsf@tines.lan> (raw)
In-Reply-To: <2849568.naTrYEPBA4@warperdoze> (Stefan Israelsson Tampe's message of "Fri, 30 Aug 2013 20:54:35 +0200")

Hi Stefan,

Stefan Israelsson Tampe <stefan.itampe@gmail.com> writes:
> Delimeted continuations can be looked upon as a generalization of
> common lisps tagbody e.g. it's trivial to produce tagbody semantics
> with the help of prompts.

I haven't yet digested the rest of your email, but I wanted to point out
that prompts are not needed to produce Common Lisp 'tagbody' semantics.
All that's needed is a set of mutually-recursive local procedures that
tail call each other.  Each local procedure corresponds to a label, and
the tail calls correspond to GOTOs.

In fact, one of the earliest papers on Scheme, "LAMBDA, The Ultimate
Imperative" published in 1976, showed how to convert arbitrary Lisp
'PROG' forms into a very early version of Scheme.  Note that Lisp 'PROG'
was a combined 'let', 'block', and 'tagbody', and can do everything that
Common Lisp's 'tagbody' can do.

    Regards,
      Mark



  reply	other threads:[~2013-08-31  4:35 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-08-30 18:54 a rehash of the question of optimizing some prompt ideoms Stefan Israelsson Tampe
2013-08-31  4:35 ` Mark H Weaver [this message]
2013-08-31  4:56   ` Mark H Weaver
2013-09-01 20:34 ` Stefan Israelsson Tampe

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