From: Robert Klemme <shortcutter@...>
Date: 2012-10-31T18:49:24+09:00
Subject: Re: bug?: local variable created in if modifier not available in modified expression

On Wed, Oct 31, 2012 at 1:53 AM, Mean L. <lists@ruby-forum.com> wrote:

> I can't say this makes sense to me.  Ruby otherwise is a dynamic
> language, but with respect to local vars it's suddenly static, and the
> parser wants to identify all local vars in one left to right parse pass,
> before the code is run.
>
> so even though at runtime
>
> (a if a = 1)
>
> local var 'a' already exists before it's read,

It could, but it doesn't - because of the current semantics. :-)

> the parser has statically
> bound the first 'a' to a method lookup path.
>
> So the question is, why in a dynamic language is local variable binding
> static?  Is it a perf optimization?

Just a guess: it's probably simpler to implement.  The decision when a
variable exists can be made solely based on textual order of the
source code and does not need to take into account how expressions are
evaluated which is a much more complicated thing to evaluate.  I
guess, Matz figured it's not worthwhile for the few corner cases.  And
the community has learned to live with it pretty well, I'd say.

Kind regards

robert


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