Re: [MacPerl] Q: How do YOU generate debugging output?

[Angus McIntyre <angus@pobox.com>]

At 8:39 am +0200 04.07.97, Alex Satrapa wrote:
>Is there "The Right Way" to enter debugging comments into code?
>
>Here's how *I* do it...
>
	[ ... snip ... ]

A wise man once said "Never underestimate the value of 'print' statements
for debugging." One refinement that I use is to hand the actual output off
to a function, something like:

  sub debug {
    my($level,$message) = @_;
    print STDERR "DEBUG: $message\n" if ($DEBUG >= $level);
  }

which can then be invoked by something like:

  &debug(2,"Oh no! We lost horribly!");

The advantage of doing it this way is that if you suddenly decide that you
want to write your debugging output somewhere else or customize the output
format, you can hack a single function rather than changing every single
invocation in the entire program. It also makes for relatively clean and
intelligible code. The actual amount of debugging information you see is
controlled by the global $DEBUG variable, and each invocation of 'debug'
specifies exactly how urgent the message in question is, so you can tailor
the output to taste.

There's probably an overhead involved in the function call (as opposed to
inlining the print statement directly) but unless you're hitting it
repeatedly in a tight loop, it's probably not important. I even leave this
stuff in 'production code', on the grounds that you never get *all* the
bugs out, and some day you may be glad of the ability to switch debugging
back on by editing a single line in a configuration file.

That's my take on it, but I'm a mere mortal in the world of Perl
programming and, given that There's More Than One Way To Do It (tm), I
await with interest to see what the Perl Gods recommend.

	A

--
angus@pobox.com                                   http://pobox.com/~angus/

"I know enough of the jargon to give me an          "Rhapsody in Black"
 excuse for anything I want to do." [Grainger]       Brian Stableford



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