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From: craig@leland.Stanford.EDU (Craig Chambers)
Newsgroups: comp.object
Subject: Re: Run-time checks, Compile time Checks, and reliability
Keywords: type checking, high reliability, fault tolerance
Message-ID: <1991Apr7.013813.23513@leland.Stanford.EDU>
Date: 7 Apr 91 01:38:13 GMT
References: <1991Mar28.161307.6071@cbnewsh.att.com> <27F780E2.1872@tct.com> <1991Apr3.203332.25348@bony1.bony.com>
Sender: news@leland.Stanford.EDU (Mr News)
Organization: AIR, Stanford University
Lines: 18

In article <1991Apr3.203332.25348@bony1.bony.com>, richieb@bony1.bony.com (Richard Bielak) writes:
|> Another argument for static type checking is that it is more
|> efficient, since many checks need only to be done once - at compile
|> time - and not millions of times at run time.

I disagree.  In a non-object-oriented language, type information does provide significant
help to the compiler, since types map one-to-one with implementations/representations.
However, in a non-object-oriented language (at least one with a good type system), types
specify interfaces (plus possibly some behavioral specifications) to objects, but 
specifically attempt to abstract away from specifying anything about implementations/
representations of the objects of particular types (to support more reusability of code).
This means that such interface-level types provide little information for a compiler to 
use to optimize messages sent to such objects.  So the standard argument that static type
information speeds execution of programs does not apply to object-oriented languages
(or at least does not apply to anything near the degree it does in non-object-oriented
languages).

-- Craig Chambers