Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!uwm.edu!bionet!agate!riacs!stanford.edu!leland.Stanford.EDU!leland.Stanford.EDU!craig
From: craig@leland.Stanford.EDU (Craig Chambers)
Newsgroups: comp.object
Subject: Re: A Hard Problem for Static Type Systems
Message-ID: <1991Apr22.221039.2719@leland.Stanford.EDU>
Date: 22 Apr 91 22:10:39 GMT
References: <1991Apr20.010347.28984@leland.Stanford.EDU> <3378@charon.cwi.nl> <1991Apr22.015415.28303@leland.Stanford.EDU> <3392@charon.cwi.nl>
Sender: news@leland.Stanford.EDU (Mr News)
Reply-To: craig@self.stanford.edu
Organization: Stanford University
Lines: 15

In article <3392@charon.cwi.nl>, guido@cwi.nl (Guido van Rossum) writes:
|> craig@leland.Stanford.EDU (Craig Chambers) writes:
|> >How does the compiler know that "<" in min will work?
|> 
|> From the definition of min it concludes that the arguments must be
|> comparable to each other.  The definition of the built-in "<" operator
|> says that two types are comparable to each other if they are the same
|> type.

The "<" message was supposed to be a user-defined message, implemented
differently by different objects/classes.  But since ABC has no
user-defined data types, this whole example doesn't make sense, and
ABC can't express the general problem I'm trying to type-check.

-- Craig Chambers