Local variables and threads

ruby-talk
1

Is there a way to ensure that a particular variable really is local to a
thread block? I have a problem with a threaded program that would be
explained if one of the local variable was actually global. I've
checked everything I can think of...

I miss my and local from perl which allowed me to explicitly control the
scope of variables.

Russell.

···

--
Posted via http://www.ruby-forum.com/.

2

Russell Fulton wrote:

Is there a way to ensure that a particular variable really is local to a
thread block? I have a problem with a threaded program that would be
explained if one of the local variable was actually global. I've
checked everything I can think of...

I miss my and local from perl which allowed me to explicitly control the
scope of variables.

Only variables prefixed with $ are global ($var and so on).
It is, however, certainly possible to have shared locals
if you have something like

  some_var

  t1 = Thread.new { ... }
  t2 = Thread.new { ... }

Any variables that you define inside the thread block will
be local to that thread, though.

Russell.

E

···

--
Posted via http://www.ruby-forum.com/\.

3

Russell Fulton wrote:

Is there a way to ensure that a particular variable really is local
to a thread block? I have a problem with a threaded program that
would be explained if one of the local variable was actually global.
I've checked everything I can think of...

I miss my and local from perl which allowed me to explicitly control
the scope of variables.

A typical problem with threads can be nicely illustrated with this:

09:21:51 [~]: ruby -e 'th=

for i in 0 .. 5
  th << Thread.new do
    sleep(rand(5))
    puts i
  end
end
th.each {|t| t.join}
'

2
5
5
5
5
5
09:22:21 [~]:

Problem here is that all threads share the local var 'i'. Solution:

09:22:21 [~]: ruby -e 'th=

for i in 0 .. 5
  th << Thread.new(i) do |x|
    sleep(rand(5))
    puts x
  end
end
th.each {|t| t.join}'

0
1
5
4
2
3

I.e. provide value(s) as arguments to Thread.new and receive them as block
parameter(s) with different name(s).

HTH

Kind regards

    robert