[plt-scheme] Questions about contracts

From: Chongkai Zhu (czhu at cs.utah.edu)
Date: Mon Apr 16 21:26:03 EDT 2007

----- Original Message ----- 
From: "Matthias Felleisen" <matthias at ccs.neu.edu>
To: "Chongkai Zhu" <czhu at cs.utah.edu>
Cc: <plt-scheme at list.cs.brown.edu>
Sent: Monday, April 16, 2007 7:04 PM
Subject: Re: [plt-scheme] Questions about contracts

>I think you're confusing an error (in PLT's contract system) with a  
> systemic flaw (in Eiffel's contract system).

Yes, this might be correct. Sorry for the confusing, but my hunch is that this will take Robby quite some effort to fix.
> Also, your error isn't repeatable:
> Welcome to DrScheme, version 369.9-svn13apr2007 [3m].
> Language: (module ...).
> > (define fred (make-array '#(#f) 8 8))
> > (define freds-diagonal (make-shared-array fred (lambda (i) (list i  
> i)) 8))
> >
> My hunch is that Robby fixed this.

Sorry, but I'm using 369.9-svn14apr2007 [3m] now, and this error still happens.

You are using the wrong language. The contract is only evoked by provide/contract. Obviously your interaction doesn't evoke any contract at all.
> ;; ---
> If I misunderstand your point, please articulate it differently. --  
> Matthias
> P.S. In the mid-90s, someone in Edingburgh published a Tech Rpt on 60 
> + flaws in SML (1.0) type system. I still claim and say in public  
> that SML is a type-safe language.


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