From: Mauricio Fernandez <mfp@...>
Date: 2007-01-11T04:05:22+09:00
Subject: Re: a most undangerous Hash#store!

On Tue, Jan 09, 2007 at 10:46:20AM +0900, Trans wrote:
> 
> Mauricio Fernandez wrote:
> 
> > Anyway, Trans was talking about destructive updates, so what about
> >
> >   def store?(key, value)
> >     unless key?(key)
> >       store(key,value)
> >       return true
> >     end
> >     false
> >   end
> >
> > similar to the #store! he described, but with a more regular behavior when you
> > have nil/false values...
> 
> well, i was thinking of combining Mr. Haines  idea with Mr. James to
> get #store_new, which seemed just about right. but now your suggestion
> is quite interesting. at first i wasn't so sure, but thinking about it
> a little more it makes sense -- "is something stored with this key? if
> not store this value with it". i was also worried that it did not
> return the stored value like the normal store, but i realize now that
> could be ambigious if value=nil, so you may be on point. is that right?

Yes, that's the idea ("more regular behavior"), but as Robert said, a
predicate method with side-effects seems _very_ dangerous (yes, store!? would
be more accurate :).

So it might make sense to name it e.g. #store_once, with the above
semantics. Returning the value that was passed to the method makes little
sense: it doesn't provide any information we didn't have to being with.

-- 
Mauricio Fernandez  -   http://eigenclass.org   -  singular Ruby