From: "ara.t.howard" <ara.t.howard@...>
Date: 2007-10-15T01:42:57+09:00
Subject: Re: Parameter in a block is not local?


On Oct 14, 2007, at 8:42 AM, SpringFlowers AutumnMoon wrote:

> I thought a iterator with a block is like an nameless function call...
> so if it is a function call, the parameter is local.
> but for the following, the output is surprising:
>
> a = 1
> p a
>
> 1.upto(10) {|a| p a}
>
> p a

one way to think about it (not entirely correct) is this

  - if the parameter exists *already* it is reused
  - if not a block local var is created

this

  1.upto(10){|a| p a}

  p a

will throw an error - as you probably know.  it's a fine line between  
having function call semantics and closure ones.  we all want this to  
work

  message = 'hello world'
  42.times{ p message }

of course. so it's rather tricky.  you can search the archives but i  
*think* the new rule is that introducing a var like so

  method{ |some_var| ...

will introduce a block local var (as you are expecting above), while  
this

  method{ p some_var

will not.  i could be confused on this though, it really gets  
confusing to not violate POLS (referring to mine here) in all cases

   http://eigenclass.org/hiki.rb?Changes+in+Ruby+1.9#l7
   http://www.davidflanagan.com/blog/2007_08.html#000137

and, of course, search the archives - matz has spelled out the  
changes several times.

kind regards.

a @ http://codeforpeople.com/
--
it is not enough to be compassionate.  you must act.
h.h. the 14th dalai lama