From: Sean O'Dell <sean@...>
Date: 2003-07-18T03:39:04+09:00
Subject: Re: What's the point?

"Chad Fowler" <chad@ns1.chadfowler.com> wrote in message
news:Pine.LNX.4.44.0307171413400.21595-100000@ns1.chadfowler.com...
> On Fri, 18 Jul 2003, Brian Candler wrote:
>
> > On Fri, Jul 18, 2003 at 02:17:42AM +0900, Phil Tomson wrote:
> > > As to your other question about "why?"  - Sometimes I used to do this
in
> > > Perl to localize some functionality within a method (..errr, function
or
> > > subroutine in Perl parlance).  Usually this was in a sort of
refactoring
> > > stage where I'd look at my sub and find that I had some duplicated
code in
> > > it that I could collect into another sub-sub.
> >
> > Beware, thar be demons.
> >
> > sub foo {
> >   my $x = $_[0];
> >   sub bar {
> >     print "x is $x\n";
> >   }
> >   bar();
> > }
> >
>
> In Ruby, the equivalent code seems to fail, with local variables not being
> accessible in nested methods.  For example:
>
> irb(main):018:0> def go
> irb(main):019:1>   1.upto(10) do |num|
> irb(main):020:2*     def my_meth
> irb(main):021:3>       puts "Printing #{num}"
> irb(main):022:3>     end
> irb(main):023:2>   end
> irb(main):024:1> end
> nil
> irb(main):025:0> go
> 1
> irb(main):026:0> my_meth
> NameError: undefined local variable or method `num' for
> #<Object:0x2b992c8>
>         from (irb):21:in `my_meth'
>         from (irb):26
>         from ?:0
>
> This seems unintuitive to me.  I would expect variables declared in a
> parent method to be accessible in child methods.  Can someone tell me why
> I'm wrong?  I'm sure I am. :)

Imagine the local function "my_meth" is defined outside of "go."  The
variable "num" wouldn't be accessible there, either.  I think "my_meth" is
thought of as a proc which just happens to be defined within "go" and not
really local to "go."  So, "my_meth" is not truly a local function then, I
think.

    Sean O'Dell