From: Guillaume Marcais <guslist@...>
Date: 2005-04-05T05:35:25+09:00
Subject: Re: Hash::MixIn and Python style Object#dict

On Mon, 2005-04-04 at 09:39 +0900, Florian Gro� wrote:
> Mathieu Bouchard wrote:
> 
> >>But I wonder: why both you and florian considered the need to have 
> >>contracts for this mixable things?
> > 
> > Because it helps distinguish responsibility in case of incorrect
> > behaviour, so that a bug can be located more easily. There's a similar
> > argument in favour of type-checking in general.
> > 
> > A way of working that many duck-typers have adopted is to just ignore
> > those things, so that all failures happen at the lowest possible level
> > instead of the highest possible one, producing error messages that are
> > meaningless in terms of the highest-level. Somehow they treat this as a
> > nonissue (and I don't want to speculate on why that is).
> 
> One thing I don't quite like about duck typing is that is applied where 
> it does not make sense to apply it.
> 
> Even the "If it quacks and walks like a duck it can be handled like a 
> duck" is an odd one. First of all duck typing never checks the "like a 
> duck" part. It also isn't correct to handle something that does a few 
> things like a duck like a duck. You can handle it like something that 
> does a few things like a duck. That's all you know.
> 
> The other area where I feel it is getting misused is calling 
> .respond_to?() duck typing. I think that duck typing has always been 
> about not checking, but rather just doing.
> 
> I guess views will widely differ on this subject and I'm not even sure 
> if there is one authorative source that could clear all these different 
> interpretations up...
> 

Do you have any example of usage of your ruby-contract library?

Guillaume.