[plt-scheme] Standard ML in PLT Scheme

From: Richard Cobbe (cobbe at ccs.neu.edu)
Date: Sat Dec 22 15:16:32 EST 2007

On Sat, Dec 22, 2007 at 11:20:16AM -0500, Sam TH wrote:
> On Dec 22, 2007 9:08 AM, Chongkai Zhu <czhu at cs.utah.edu> wrote:

> > 2.Dynamically typed code is the only thing available in PLT at run time.
> > Even typed Scheme turns everything into a dynamically typed world after
> > static type checking.

> This is true, but somewhat misleading.  Every programming language,
> typed or untyped, is ultimately executed on the untyped processor.

To borrow a phrase, this is true but irrelevant.  :-)

The untyped processor (at least on modern stock hardware like ppc or i386)
doesn't unconditionally and automatically insert tag checks that are
unnecessary if your source language has a sound type system.  This is what
I understood to be the point of Tomi Neste's question up-thread.

Marco Morazan hasn't stated his objections to dynamic typing, but that
phrase as I've seen it used usually implies the existence of these tag
checks.  (I think the Perl folks use it to refer to duck typing, but I also
think they're obscuring an important distinction.  For the current
discussion, though, this doesn't matter, as stock processors don't do those
auto-coercions either.)

Or am I misunderstanding you, Marco?

In any case, I think the untyped-ness of the underlying hardware is a


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