> I wonder if I could run an idea I've had by this list. It seems to
> me you could get some of the desired effects of lazy evaluation by using
> continuation passing style in code. For example, take this psuedo-code
> using CPS to represent an infinite data type.
This has been known for a long time; the CPS translation results in a
program that has the same behaviour no matter what the underlying
language's evaluation semantics are. The lambdas make explicit what
can happen now and what must be delayed until later. Consequently
using a strict (call-by-value) or lazy (roughly call-by-name) language
makes no difference.
Here is what I believe to be the original paper (1975):
@Article{
Plotkin75:Call,
author="G. D. Plotkin",
title="Call-By-Name, Call-By-Value and the Lambda Calculus",
journal="Theoretical Computer Science",
year="1975",
volume="1",
pages="125--159",
abstract="This paper examines the old question of the relationship
between ISWIM and the $\lambda$-calculus, using the distinction
between call-by-value and call-by-name. It is held that the
relationship should be mediated by a standardisation theorem.
Since this leads to difficulties, a new $\lambda$-calculus is
introduced whose standardisation theorem gives a good
correspondence with ISWIM as given by the SECD machine, but
without the \emph{letrec} feature. Next a call-by-name variant of
ISWIM is introduced which is in an analogous correspondence with
the usual $\lambda$-calculus. The relation between call-by-value
and call-by-name is then studied by giving simulations of each
language by the other and interpretations of each calculus in the
other. These are obtained as another application of the
continuation technique. Some emphasis is placed throughout on the
notion of operational equality (or contextual equality). If terms
can be proved equal in a calculus they are operationally equal in
the corresponding language. Unfortunately, operational equality
is not preserved by either of the simulations.",
}
Enjoy!
--KW 8-)
--
Keith Wansbrough <[EMAIL PROTECTED]>
http://www.cl.cam.ac.uk/users/kw217/
University of Cambridge Computer Laboratory.
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