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From: new@ee.udel.edu (Darren New)
Newsgroups: comp.object,comp.lang.misc,comp.lang.eiffel
Subject: Re: A Hard Problem for Static Type Systems
Message-ID: <51986@nigel.ee.udel.edu>
Date: 26 Apr 91 22:23:22 GMT
References: <1991Apr20.010347.28984@leland.Stanford.EDU> <554@eiffel.UUCP>
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In article <554@eiffel.UUCP> bertrand@eiffel.UUCP (Bertrand Meyer) writes:
>by craig@leland.Stanford.EDU (Craig Chambers):
>> Here's the problem: we'd like to describe the type of the min
>> function
>one could define `min' in that class as
>	min (other: like Current): like Current is

Doesn't look like you've answered the question here.  What's the type of `min'?
All you've shown is how Eiffel can express restrictions on the patterns of
inputs that min can accept and the type that min will return given certain
input types.  You have not said what the type of min is.  In Smalltalk,
I can say

Class 		Mary 
method 		zelda: thing
code		^ thing

and say that the zelda: message will always return the same type as its
argument.  That doesn't make Smalltalk statically typed.

I'm not bashing Eiffel.  I don't even know Eiffel.  Maybe the response would
be obvious if I *did* know Eiffel.  But so far, it looks like `min' is
a dynamically-typed function.  (Either that, or it is a polymorphic function,
at which point the *declaration* is dynamically typed and the *application*
is statically typed; i.e. "min(other : like Current)" is dynamically typed,
but "min(3,5)" is statically typed as an integer and "min(<<3,4>>,<<5,6>>)" is
statically typed as a list.)
	   -- Darren

-- 
--- Darren New --- Grad Student --- CIS --- Univ. of Delaware ---
----- Network Protocols, Graphics, Programming Languages, FDTs -----
+=+ Nails work better than screws, when both are driven with hammers +=+