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From: kennel@lyapunov.ucsd.edu (Matt Kennel)
Subject: Re: Static vs. Dynamic typing again (was Re: OO, C++,
 and something much better!)
Date: 1997/02/10
Message-ID: <5dmj1v$jhk@news1.ucsd.edu>#1/1
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references: <JSA.97Jan16141937@alexandria> <32E7E08A.3079@parcplace.com>
 <32E8BCE3.3029@calfp.com> <01bc0a1e$faed8ce0$c318b993@jarvisb>
 <E4L15n.GnC@world.std.com> <5covaj$l0@boursy.news.erols.com>
 <yf37mkiiwe1.fsf@sabi.demon.co.uk>
followup-to: comp.lang.smalltalk,comp.lang.eiffel,comp.lang.ada,comp.object
organization: The University of California at San Diego
newsgroups: comp.lang.smalltalk,comp.lang.eiffel,comp.lang.ada,comp.object
Date: 1997-02-10T00:00:00+00:00
List-Id: <comp.lang.ada>


Piercarlo Grandi (piercarl@sabi.demon.co.uk) wrote:
: >>> "feldmand" == Damon Feldman <feldmand@erols.com> writes:

: >> I think it's a bit misleading to say that Smalltalk is dynamically
: >> typed versus Ada/C++/etc being statically typed.  I mean, Smalltalk
: >> does not check the type of an object when passing it as a parameter

: feldmand> Statically typed means that types are *determined* at compile
: feldmand> time.

: Consider:

:   class A { ... }; class B : A { ... };
:   class A a; class B b; class B *bp;

:   bp = (randomNumber() > 0.5) ? &a : &b;

: Here there is no question that 'bp' has a static type constraint, and
: also no question that it is impossible statically to infer the type of
: object denoted by 'bp' after the assignment above.

I don't know for sure, but what about a system where a
'routine feature' could be added to a class during the execution
of a program, so that at one point in time, an object of such class
would not be compatible with some interface (e.g. not ''type'' T)
but at a later time the 'same object' (forbearing us the common delusion
that objects have identity :) ) would be compatible with that interface.