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From: cs450a03@uc780.umd.edu
Newsgroups: comp.lang.misc,comp.object
Subject: RE:  Type Systems and Dynamic Binding
Message-ID: <17APR91.21054415@uc780.umd.edu>
Date: 17 Apr 91 21:05:44 GMT
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Dan Bernstein writes:

>For each EXAMPLE of dynamic typing that people put up, I showed how
>it would typically be implemented (directly) in C. I hope you can see
>the difference between this and what you're talking about.

heh heh heh... Excellent :-) 

 f(x, y)
LIMIT ERROR

------------------------

Let's say I was trying to implement a dynamically typed language in C.
(Of course, I wouldn't _really_ be that crazy  :-)  Let's say I wanted
to detect when, for instance, the addition of 2 integers produces an
invalid result.  Let's say that I can not accept a severe performance
hit for this checking (most of the time, it's not going to happen.
When it does happen, I'm going to switch to float -- performance must
be better than floating point).

Now, I know that this sort of information is available if I was
working in assembly (I'm not working on a pathologically silly
machine).  But how would I do it in C?  As near as I can tell, C just
throws the information away.

This is a _very_ simple sort of test.  I'd want to detect erroneous
results for every primitive expression I built into the language.
These tests would be less significant (in terms of time and space)
than simple housekeeping (loads and stores, loop management, etc.) if
I were working in assembly.

How do I do it?

Raul Rockwell