From: djd15@...
Date: 2003-08-07T23:18:17+09:00
Subject: Re: C's static equivalent

More or less:

def make_closure
   perm_variable = 0
   return proc {
      perm_variable += 1
      puts "I have been called ", perm_variable, " times."
   }
end

def use_closure
   fun = make_closure
   fun.call
   fun.call
   fun.call
end

use_closure

Should print out

   I have been called 1 times.
   I have been called 2 times.
   I have been called 3 times.

However, each time you call make_closure, it returns a separate context, so:

def use_closure2
   fun1 = make_closure
   fun2 = make_closure

   fun1.call
   fun2.call
   fun1.call
end

use_closure2

Should print:

   I have been called 1 times.
   I have been called 1 times.
   I have been called 2 times.

Because fun1 and fun2 store two separate states of perm_variable.
At least that's my understanding of closures.

As far as I know, there's nothing quite like C's static
in Ruby, since there's no way to make a variable local
in scope to a function, but persistant in state over all
calls to that function (at least that I know of).

- Dan

----- Original Message -----
From: KONTRA Gergely <kgergely@mlabdial.hit.bme.hu>
Date: Thursday, August 7, 2003 9:59 am
Subject: Re: C's static equivalent

> On 0807, ts wrote:
> > >>>>> "K" == KONTRA Gergely <kgergely@mlabdial.hit.bme.hu> writes:
> > 
> > K> Is there something similar to C's static keyword?
> > K> I want a single function, which has to access and modify a 
> permanent> K> variable. Any solution without bundling the function 
> to a class?
> >  Use a closure
> Could you be more verbose? Eg. how to print out how many times a
> function was called.
> 
> Gergo
> -- 
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