Subject: Re:
From: Craig Chambers (chambers@cs.washington.edu)
Date: Tue May 09 2000 - 14:35:18 PDT
mayur@crosswinds.net wrote:
>
> I have a query concerning constructing dispatchers for programs
> written in a language like Cecil which allows mixed statically-
> and dynamically-typed code by virtue of its optional static type
> system built on a dynamically-typed core.
>
> Suppose a statically-typed Cecil program has 2 sets of methods
> such that:
>
> 1. All methods have the same name and number of args.
> 2. One set of methods conforms to signature X and the other
> conforms to signature Y.
>
> Do you generate 2 dispatchers (one for messages conforming to
> sign X and the other for messages conforming to sign Y) or do
> you generate just one dispatcher which uniformly handles both
> kinds of messages?
>
> One would follow the former approach if the language were purely
> statically-typed and the latter if it were purely
> dynamically-typed. But what does one do when the program is
> written in a language like Cecil? I believe there are three
> approaches:
>
> 1. Follow the latter approach indiscriminately.
This is what we did in the experiments reported in the OOPSLA'99 paper. All of
Vortex ignores static type declarations, and instead applies a kind of type
inference (aka class analysis) to deduce a kind of type declaration useful to
the compiler, i.e. a set of concrete classes for each variable & expression.
> 2. Provide a compile time option which allows the programmer to
> indicate whether the program is purely statically-typed.
> If it is, the compiler can take advantage of the former
> approach. If it isn't, the compiler uses the latter
> approach irrespective of whether the program is purely
> dynamically-typed or mixed statically- and dynamically-typed.
> 3. The compiler should be smart enough to determine when to
> follow the former approach and when to follow the latter.
> This is probably not feasible.
>
> Could you please comment on the above? Thanks for your time.
>
> -- Mayur
The paper also discusses specializing dispatchers based on available static type
information. This includes the possibility of specializing based on available
static class information, which in general subsumes your proposal to specialize
based on signatures.
-- Craig Chambers
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