From: Florian Gross <flgr@...>
Date: 2004-07-19T08:02:29+09:00
Subject: Re: Current method

James Britt wrote:

> Here is an example based on something I believe Rick Kilmer posted here 
> some time ago, plus some additional neat Ruby magic for dynamic code 
> tracing (also from Rich, I think, but I might be wrong on that).
> 
> # Eval a code block using the original context of the variables
> def trace( &block )
>   expr = block.call
>   puts "trace: #{expr} = #{eval(expr, block)}"
> end
>   trace { "x + y + z" }  # Show this to Java(tm) fans.

Using Binding.of_caller (available from 
http://noegnud.sourceforge.net/flgr/binding_of_caller.rb) this can be 
simplified to  trace "x + y + z":

require 'binding_of_caller'

def trace(expr)
   Binding.of_caller do |context|
     result = eval(expr, context)
     puts "trace: #{expr} = #{result.inspect}"
     return result
   end
end

I'm using it like this:

irb(main):026:0> x = 2; y = 3; trace "(x + y) ** (x * y)"
trace: (x + y) ** (x * y) = 15625
=> 15625

Regards,
Florian Gross