From: Markus <markus@...>
Date: 2004-09-17T03:36:45+09:00
Subject: Re: Changing outside variables inside a proc

On Thu, 2004-09-16 at 10:28, Nate Smith wrote:

> Is there any way to change an outside-scoped object inside a proc? Such
> as:
> 
> a = "Foo"
> b = "bar"
> proc = Proc.new { |val1, val2| val1, val2 = "boo", "baz" }
> proc.call( a, b )
> 
> # a and b are still "Foo" and "bar"
> 
> I don't believe this is possible.. but would be very nice for creating a
> collect! method for a user-defined object. Thanks

     I suspect you are right (that it isn't possible), at least without
going through some rather extreme contortions.  Over all, I'm _glad_
that this is the case (though I must admit I've past parameters in "var"
with wild abandon in other languages).

     Why do you think this is needed (or nice) for writing a collect!
method?  Why cant you just write something like:

    class My_collection_class
        def [](k)
            :
            end
        def []=(k,v)
            :
            end
        def each_key
            :
            end
        def collect!
            each_key { |k| self[k] = yield(self[k]) }
            end
        end

 -- MarkusQ