From: Gavin Sinclair <gsinclair@...>
Date: 2004-08-18T08:13:58+09:00
Subject: Re: Getting the binding of the caller

On Wednesday, August 18, 2004, 8:52:18 AM, Michael wrote:

> Hi,

> Is there a way to get the binding of the caller?

>    class A
>      def m(b=binding)
>        eval("self", b)
>      end
>    end

>    A.new.m           # => #<A:0x81e1bec>
>    A.new.m(binding)  # => main

> What I want is exactly the second, but without specifying "binding" 
> explicitly.

> Possible or not?

It's been discussed on -talk this year, so a search in the archive for
'binding' should help.  Someone posted a continuations-based solution
that gives you basically what you want, but at considerable runtime
expense, IIRC.

There's no plain-Ruby solution; i.e. the language doesn't go out of
its way to help you here.  There's an RCR for it; can't remember which
one.

However, blocks can be useful here, and may just be good enough for
you.

  def trace(&block)
    expr = block.call
    value = eval expr, block
    puts "#{expr} = #{value}"
  end

  def foo
    x = 5
    y = 12
    trace { "Math.sqrt( x**2 + y**2 )" }
  end

I gotta say that's pretty handy.

Cheers,
Gavin
    
--
Gavin's vim tip for the day: ':help text-objects'