🚀 go-pugleaf

In article <BEVAN.92Apr10173700@panda.cs.man.ac.uk> bevan@cs.man.ac.uk (Stephen J Bevan) writes:
|In article <s37hvINN1j1@network.ucsd.edu> mbk@lyapunov.ucsd.edu (Matt Kennel) writes:
|   bevan@cs.man.ac.uk (Stephen J Bevan) writes:
|   : In article <1992Apr8.180420.9294@newshost.lanl.gov> jlg@cochiti.lanl.gov (Jim Giles) writes:
|   :    The word `type' has no meaning at all if all attributes are
|   :    dynamically alterable.
|   : 
|   : I would have thought it did, the "type" is just the "type" at the
|   : particular time you look at it.  I'd consider this "dynamic typing".
|
|   Well in that case all you mean by "type" is some sort of "hidden value" that
|   hangs on with the object that affects what it means in any given
|   expression.
|
|Logically this is true for most languages.  It is only in the
|implementation of certain languages that _static_ information from the
|program text can allow the "hidden value" to be optimised away.

Nononono! If this were an accurate description, then the type would be
stored in a field (possibly optimisaed away!) whose type was described
by a field of type ? and value "type", whose type is described by a
field of type ?? and value ?, whose type is described by a field of
type ??? and value ??, whose....

So you have to do an INFINITE amount of optimisation to get a finite
programme.

But infinite optimisations and infinite programmes are, um, tricky
formal objects. Are you really *sure* this is how you want to approach
the issue?

"Type" is the information that must be available BEFORE manipulating a
value. And it is always grounded somewhere: in the language
specification. The length of the chain between the spec and the bits
in the machine, may, however, vary according to your driving habits.
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stephen p spackman         Center for Information and Language Studies
stephen@estragon.uchicago.edu                    University of Chicago
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