From: dblack@...
Date: 2007-09-04T05:34:22+09:00
Subject: Re: Ruby stupidities

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Hi --

On Tue, 4 Sep 2007, Matthias W=E4chter wrote:

> dblack@wobblini.net schrieb:
>>> But certainly this may break existing libs, so be careful.
>>
>> The problem is, you can't be careful. You can only decide that it's OK
>> for code to break, and keep your fingers crossed that it doesn't.
>
> Sure. Whenever you extend a basic class you take the risk of
> breaking something. Choosing a name for a function or an alias when
> you extend a function is nontrivial if you want to take into account
> that the name can already be used.

I guess what I wonder is: what does it mean to take that into account?
If it affects our decisions, then we should always decide not to --
and all the more for actually changing the behavior of existing
methods.

>> I don't mean to split hairs -- of course "careful" can mean lots of
>> things. It's just that I think it's important to remember that the
>> code doesn't "know" that the person who changed it is worried :-)
>
> :)
>
>> It's
>> just going to do what it does. So unless you're willing to read
>> through the entire source code base, for Ruby and all add-on
>> libraries, every time you make such a change, you're pretty much
>> accepting some very real risk.
>
> I think that is what everyone who writes libraries has to do for
> 1.9/2.0 anyway.

I definitely don't discourage reading through the source :-) But it's
very hard to check reliably to see (for example) whether there's any
case where someone relies on the behavior of String#[], or gsub!
returning nil, or whatever. And it could change....

I have to add that I'm just thinking out loud about things that have
been tossed around for years -- it's not really a specfic critique of
what you said, more that I've never quite understood what it actually
*means*, in practical terms, when people say that one should be
careful about making core changes, or not do it lightly, or "With
great power comes great responsibility", etc. It's partly why I like
#extend so much -- it limits the changes to individual objects.


David

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