Undefined local variable?

Ruby
1

Dear All,

Why is there still NameError?

ruby-1.9.2-p0 > l = ->{ h }
=> #<Proc:0x000001009d7eb0@(irb):1 (lambda)>
ruby-1.9.2-p0 > l.call
NameError: undefined local variable or method h' for main:Object from (irb):1:inblock in irb_binding’
from (irb):2:in call' from (irb):2 from /Users/siegfried/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in’
ruby-1.9.2-p0 > h = 1
=> 1
ruby-1.9.2-p0 > l.call
NameError: undefined local variable or method h' for main:Object from (irb):1:inblock in irb_binding’
from (irb):4:in call' from (irb):4 from /Users/siegfried/.rvm/rubies/ruby-1.9.2-p0/bin/irb:17:in’

Best regards,
Zhi-Qiang L.
[email protected]

2

Hi,

In message “Re: Undefined local variable?”
on Fri, 24 Dec 2010 14:29:36 +0900, Zhi-Qiang L.
[email protected] writes:

|Why is there still NameError?

Because name resolution for local variables are done in compile time.

          matz.
3

Hi Matz,

Can I refresh it?

On Dec 24, 2010, at 1:45 PM, Yukihiro M. wrote:

Best regards,
Zhi-Qiang L.
[email protected]

4

Hi,

In message “Re: Undefined local variable?”
on Fri, 24 Dec 2010 14:48:41 +0900, Zhi-Qiang L.
[email protected] writes:

|Can I refresh it?

Basically, no.

          matz.
5

Yukihiro M. wrote in post #970434:

Hi,

In message “Re: Undefined local variable?”
on Fri, 24 Dec 2010 14:48:41 +0900, Zhi-Qiang L.
[email protected] writes:

|Can I refresh it?

Basically, no.

          matz.

That’s true; if h wasn’t a local variable at the time the proc was
defined, then it is compiled as a method call.

But as an aside, you can change the value of h if it was a local
variable at the time, even if it is no longer in scope.

ruby-1.9.2-p0 > def foo
ruby-1.9.2-p0 ?> h = 4
ruby-1.9.2-p0 ?> ->{ h }
ruby-1.9.2-p0 ?> end
=> nil
ruby-1.9.2-p0 > l = foo
=> #<Proc:0x00000002229500@(irb):8 (lambda)>
ruby-1.9.2-p0 > l.call
=> 4
ruby-1.9.2-p0 > eval “h=5”, l.binding
=> 5
ruby-1.9.2-p0 > l.call
=> 5

So maybe your solution is to do “h = nil” before defining the proc.