From: Daniel DeLorme <dan-ml@...42.com>
Date: 2008-10-02T14:26:44+09:00
Subject: Re: ruby1.9 block scope

Suraj Kurapati wrote:
> Brian Candler wrote:
>>   def my_find(a)
>>     # res=nil not needed!
>>     a.each { |e| res = e if e =~ /foo/ }
>>     res
>>   end
> 
> IMHO, the res=nil is necessary to preserve the semantics of a closure:
> 
> A lambda/closure should *enclose* the variables around it into a neat 
> package.  It should *not* emit new variables into its surroundings! 
> Otherwise, it would be something like an "opener" instead of a 
> "closure".

If you're thinking in terms of lambdas and anonymous functions then I 
can see how you would think that. But I think of blocks more in terms of 
control structures. Variables defined inside a "if" or "while" statement 
continue existing outside of the if/while, and so should variables 
defined inside a block.

I don't deny that that lambdas are useful, but I do think we have a 
conflict here: blocks are used both as control structures and as 
lambdas, and those two would benefit from having different scoping rules.

--
Daniel