From: Sean O'Halpin <sean.ohalpin@...>
Date: 2009-02-03T08:33:22+09:00
Subject: Re: Is this possible in Ruby

On Mon, Feb 2, 2009 at 10:49 PM, Damjan Rems <d_rems@yahoo.com> wrote:
>
> Just an idea which may come in handy. Can this be done and how in Ruby.
>
> def calc(what)
>  some_eval(what)
> end
>
> a=10
> b=12
> calc('a+b') # expression as parameters
> => 12   # would return
>
> a='aa'
> b='bb'
> calc('a+b')
> => 'aabb'
>
> This is of course strictly hypothetical. I would like the expression to
> be evaluated inside the method using variables which are local to the
> calling part.
>
>
> by
> TheR

ruby 1.9 comes with Binding#eval. In 1.8.6 you can do this:

class Binding
  def eval(str)
    Kernel.eval(str, self)
  end
end

a = 10
b = 12
binding.eval('a + b') # => 22

def another(c, d)
  binding.eval('c + d')
end
another(20, 22) # => 42

Regards,
Sean