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From: cs450a03@uc780.umd.edu
Newsgroups: comp.lang.misc
Subject: RE: Dynamic typing (part 31,497)
Message-ID: <24APR91.08062530@uc780.umd.edu>
Date: 24 Apr 91 08:06:25 GMT
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Norman Diamond:
David Gudeman:

>>... static typing implies ... all expressions can be assigned types
>>from a restricted set ... such that machine representations can be
>>decided on at compile time 

>Yes.

>>                           and such that no type information has to
>>be associated with a value at runtime.

>No.

No, "type information has to be associated with a value at runtime" ?

Then what is dynamic typing?

Or, was this a statement that "constant type tags can be assiciated
with a value at runtime"?  If so, it is far from a clear statement.

>Why not both [dynamic and static typing] ?

"Both" is, by definition, not static typing -- such a language would
allow you to express statements which can not be statically typed.  On
the other hand, it is often a simple matter (of strength reduction) to
extract static typing information from statements in a dynamically
typed language.

One distinction is that in a dynamically typed language type
assertions are "just another operator" and most likely will use the
same syntactic conventions as other language operators.  In statically
typed language this does not have to be the case, and usually is not.

This was hashed out in comp.lang.misc about a month ago, though it
might not have been expressed fully in any one article.

Raul Rockwell