From: Ross Bamford <rossrt@...>
Date: 2006-02-28T22:40:33+09:00
Subject: Re: Subclassing Struct.new

On Tue, 2006-02-28 at 22:14 +0900, chiaro scuro wrote:
> On 2/28/06, Ross Bamford <rossrt@roscopeco.co.uk> wrote:
> > This local variable isn't yet initialized (the n + 1 would be it's
> > initializer), so n + 1 ends up being nil + 1, or (effectively) nil.+(1),
> > hence the "undefined method '+' for nil:NilClass".
> >
> > Using self.n = 1 forces Ruby to treat the assignment as involving the
> > method 'n' on 'self'.
> >
> > I don't think it's a bug, but I know it's tripped people (including me)
> > up before. From the implementation point of view it's probably the
> > lesser of two evils, though.
> 
> It's really unrubesque and tricky.  What would be the consequences of
> handling it as you would normally expect?  What would the side effects
> be?
> 

This isn't necessarily based in fact (i.e. I've not surfed the source
just now) but I imagine it would be:

	* Harder to parse, with more ambiguous cases.
	* Generally slower, since local lookup would be 'the long way'
	  more often.
	* More difficult to follow the code six months down the line 
	  (or on the next guy's screen).

-- 
Ross Bamford - rosco@roscopeco.REMOVE.co.uk