From: Tom Sawyer <transami@...>
Date: 2003-02-14T16:20:23+09:00
Subject: Re: Lexical scope and closures

On Thursday 13 February 2003 08:03 pm, Yukihiro Matsumoto wrote:
>   arr.each {|i|
>     local{|a,b|
>       c = ..
>       ...
>     }
>   }

mmm...seems overly syntatical, might as well do:

  arr.each {|i;a,b|
	c = ..
  }

though for some reason i don't like this either. feels like a aand b should be 
catching something, not just becoming local.

>   arr.each {|i|
>     let a = ..
>     let b = ..
>     c = ..
>     ...
>   }

clean, though this is a declarative, which i thought you were trying to avoid. 
but maybe this is best. yet i think this would add complication: what would 
'let' mean outside of block? wouldn't one be inclined to have it go further:

  class A
    def inititalize
      c = "instead of @c"
      let a = "instead of just a"
    end
  end

which might be all well and good, but i think it's a little too late for this. 
so unless you really wanted to do this despite code breakage, 'let' and ':=' 
should probably be avoided --the inclination toward the above would be too 
strong.

yet, something drives me to want procs and blocks to be like methods --that 
everything is local and you have to pass variables in and out, but this 
doesn't coincide well with current ruby, and perhaps defeats the purpose of 
closures.

hmmm... might as well throw this out:

  arr.each do(a,b) |i|
    c = "is local"
    a = "not local"
    b = "not local"
    d = "is local"
    return d   # but this gives d to outer scope
  end

another idea to add to the pool.  give it plenty of time, the best solution 
will clearly arise at some point. who knows, perhaps you got it right the 
first time: the way it is ;-)

-- 
tom sawyer, aka transami
transami@transami.net