From: Robert Klemme <bob.news@...>
Date: 2004-02-26T18:39:49+09:00
Subject: Re: [ot] proposal: debug keyword


"Charles Comstock" <cc1@cec.wustl.edu> schrieb im Newsbeitrag
news:c1jbfq$eiv$1@newsreader.wustl.edu...
> Simon Strandgaard wrote:
>
> > On Wed, 25 Feb 2004 15:38:53 +0100, Robert Klemme wrote:
> >
> >>"Simon Strandgaard" <neoneye@adslhome.dk> schrieb im Newsbeitrag
> >>
> >>>Any ideas for a good name?
> >>>
> >>>debug replacement puts  ->  #debug_puts,  #dputs
> >>>debug replacement p     ->  #debug_p,     #dp
> >>
> >>Hm...  I'd go for "d_puts" which is immediately distinguished from
"puts"
> >>but is not so much typing overhead as the more verbose "debug_puts".
> >>
> >>
> >>>maybe just turn the 'p' in 'puts' upsidedown, so it becomes a 'd' =>
> >>
> >>duts?
> >>
> >>http://www.best-lyrics-zone.net/Upside_Down_Lyrics.html
> >>:-)
> >>
> >
> >
> > BTW: I had to change my taste of music so it reflect the language I am
using
> >
> > diamonds are forever
> > lucy in the sky with diamonds
> > diamonds are a girls best friend
> >
> > --
> > Simon Strandgaard
>
> It would be nice if we had macros for the debug stuff, so the code would
> never even be seen when you didn't do debug code.  For instance if
> instead for debug output you had a debug block, which was evaled and
> added to the code on the first pass, so it would execute all further
> passes.  This would only occur if $debug was set, otherwise the code
> would never be evaled, and we wouldn't even test to see if the verbose
> flag was set, and thus it would never actually get executed.  I suppose
> this could also be simulated if we had constant propagation in the
> interpreter, so that a constant if expression would be eliminated.

I don't mandate a preprocessor since Ruby is flexible enough and we all
know what Bjarne said about one of his biggest mistakes with C++... :-)

IMHO this is as efficient as it can get without a macro preprocessor.  The
overhead is a single method call and a boolean test for non debug mode:

module Kernel
  def debug
    yield if $DEBUG
  end
end

Then you can do:

def foo
  debug {
    # complex calculations might be here
  }

  # normal operation
end


> Another comment though, I really hate having only the ability to turn
> debug output off globally.  It's much nicer to be able to turn it all on
> or off, but also be able to turn it on per the scope you are in.

That's what Simon's suggestion was all about. :-)

    robert