From: matz@... (Yukihiro Matsumoto)
Date: 2003-01-30T22:26:31+09:00
Subject: Re: Local variables & blocks

Hi,

In message "Re: Local variables & blocks"
    on 03/01/30, YANAGAWA Kazuhisa <kjana@dm4lab.to> writes:

|So in the following:
|
|    # until here, there's no foo.
|    10.times do
|      Thread.new do
|        # long, time-varying process without foo.
|
|        foo = Foo.new
|    
|        # process using foo.
|      end
|    end
|
|Do all new threads (and of course the main thread) share variable foo
|and their accesses are interleaved arbitrary?  Well in that case we
|still use block parameter as block local variable but that's little
|quirky.

Yes.  You will need to introduce block local variables explicitly, for
example

    10.times do
      Thread.new do
        # long, time-varying process without foo.
        local do |foo|       # "local" is merely a method name
          foo = Foo.new
          # process using foo.
        end
      end
    end

or maybe more compactly

    10.times do
      Thread.new do
        # long, time-varying process without foo.
        let foo = Foo.new
        # foo is available to the end of scope
        # process using foo.
      end
    end

|I heard once that that is one of current behavior --- a variable
|appears first in a block, that variable is localized for the block.

It is true (the primary reason was to implement lambda).  But result
was not as good as I expected.

							matz.