From: Eric Mahurin <eric_mahurin@...>
Date: 2005-09-10T02:34:40+09:00
Subject: Re: quick print type debugging

--- Florian Gro� <florgro@gmail.com> wrote:

> Eric Mahurin wrote:
> 
> > What would be nice is if you could somehow convert the
> block
> > back to text (and put it in the debug message).  Anybody
> know
> > how to do that?  I know I could make the block be a string
> of
> > the code instead to solve the problem (d{"..."}), but that
> > would be uglier and less efficient when we have debugging
> off
> > (because we have to eval).
> 
> See attachment. It's not very general, though.

Perfect.  This was from a ruby quiz, right?  Now here is the
new method (didn't need binding_of_caller.rb):

require 'proc_source.rb'

$DEBUG_LEVEL = ENV['DEBUG']||0

module Kernel
  def d(level=1,&block)
    if $DEBUG_LEVEL>=level
      ret = yield
      filename,lineno = block.source_descriptor
      $stderr.printf("DEBUG: %s:%d {%s} => %s\n",
        filename,lineno,block.source,ret)
      ret
    else
      yield
    end
  end
end


$DEBUG_LEVEL = 1
x = d{1+2} + 3*4 - d{5/6}

DEBUG: (irb):24 {} => 3
DEBUG: (irb):24 {} => 0
=> 15

Didn't work.  Any idea why, Florian?  I tried aProc.source
after using lambda to create it and it worked (also in irb). 
But, with a block it doesn't seem to.


> I think I'd go with the string solution, use
> Binding.of_caller to put it 
> into the right context and alias it to a method that does
> nothing when 
> $DEBUG isn't set.

I need to evaluate the block even without debugging because the
result will be used as part of an expression independent of
debugging mode (see above).



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