From: Brian Candler <b.candler@...>
Date: 2011-04-19T17:05:53+09:00
Subject: Re: anonymous closures with Proc,new, lambda and ->

Stu wrote in post #993687:
> I am new to the study of functional paradigm. If this question is
> academic
> please bear with me.
>
> How would I make this counter with lambda or -> without deferring to a
> named
> generator method or sigil var?

Starting with the "named generator method":

def make_counter(init)
  lambda { init += 1 }
end

Calling that method creates a new scope, and binds the value of 'init' 
within that scope.

Now, you can do the same without def, by wrapping in another lambda:

counter_maker = lambda { |init| lambda { init += 1 } }
c = counter_maker.call(100)
c.call  # 101
c.call  # 102

And you can do the same without explicitly binding 'counter_maker' 
either:

c = lambda { |init| lambda { init += 1 } }.call(200)
c.call  # 201
c.call  # 202

Is that what you were looking for?

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