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Re: the forward method [dynamic vs. static typing]

Peter van Rooijen wrote:

> From: "Joe Marshall" <jrm@ccs.neu.edu>
>>John Clements <clements@brinckerhoff.org> writes:
>>>Typically, type systems help you to construct a proof that certain
>>>errors cannot arise during evaluation.  When parts of that proof are
>>>used to alter the evaluation itself, you suddenly have a class of
>>>_runtime_ errors (or rather, "mis-behaviors") that can only be
>>>understood by examining the type proof.
>>I think that John has identified what it is that made me uncomfortable
>>with this style.  I generally think of the type system as meta
> Based on this I started to wonder, "what exactly is the goal of a type
> system?" and quickly googled for "goal of a type system" and found an
> interesting variety of insights, and on "goals of a type system" and found
> what I quote below in :

There's something wrong with the wording of that question IMHO.

It's not that some people sat together, wrote up some requirements for 
something they later called "type system", and then tried hard to 
implement these requirements.

It's more that it's somewhat natural to implement static checking in 
certain ways, and that people later realized that this can have certain 

These are not goals, these are effects.


Pascal Costanza               University of Bonn
mailto:costanza@web.de        Institute of Computer Science III
http://www.pascalcostanza.de  Römerstr. 164, D-53117 Bonn (Germany)