Well, if you can't see the small parts, work from top down first. I've often coded things as:

my $data = get_data();
process_data($data);
print_result();
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literally, as if it were pseudo code. Then I write stub routines, like:

sub get_data {
  # returns scalar data pointer to my structure
  my $return_value;
  my $db = open_database($credentials); # must declare this above
  my $data = query_db($db, "select * from bar");
  $return_value = massage_data($data);
  return $return_value;
}

sub open_database {
  my $cred = shift;
  warn "open_database doing nothing";
  return undef;
}
...
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and so on... Then at any time, I can "run" what I've got. And stay focussed on each area of development. If I need a class, I'll develop a generic class that I can plug in.

Again, the goal is to type a dozen-ish lines of code, then invoke it. That's nearly always been possible.

-- Randal L. Schwartz, Perl hacker

You probably meant this one. :)

...except that it's a little bit more difficult in, for example, GUI programming. ie. It's not always easy to draw up a whole new form to test something out. For smaller, command-line and CGI's it should always be feasible to pull some piece aside though and examine it (I find Python's interactive prompt nice for this too.)

This does sound so basic, but I still forget this fairly often. :)

Agreed. Quality over speed is most often the right path to take, IMHO. Like the previous point cited though, this too may be oft forgotten.

You're in an ideal position to have perspective on this, since you have a history of contact with students.

What trends are you seeing in their approach to debugging?

Well, for one, I deliberately don't waste time teaching the Perl debugger in the llama course (or in the llama book). Frankly, if you need to invoke a debugger on a 10-line program, you should not be a programmer.

So, I see two kinds in the llama class. People who work like me, and people who don't. Most of the people who work like me (little snippets, until it works) get the job done quickly. Most of the people who don't seem to get into cut-n-paste frenzy, and then unable to continue with the later exercises where we talk more about concepts and show fewer working programs.

I'm rethinking the strategy for the PROM course (packages references objects modules), simply because the "x" output from the Perl debugger is durn useful at just seeing what you autovivified. I have a "long" version of the course where I teach the debugger toward the end, but I've ended up demo-ing it in the middle instead far too often.

Personally, my use of the debugger is limited to "perl -debug", to try out one line snippets interactively. I remember that neither Larry nor I had enough experience with the Perl debugger (even though he wrote it!) for the first Camel, and that's why there's very little on the debugger in there. Neither of us use it!

-- Randal L. Schwartz, Perl hacker

since you have a history of contact with students.

I just realized that this statement taken out of context could send me up the river for a while.

This morning, I found that amusing. {grin}

-- Randal L. Schwartz, Perl hacker

Always have a testable version that's no more than a dozen lines different from the one you're working on. Then you'll know your error is always within the last dozen lines of code you wrote.

I read this and I think "shell script". Do you have a set of tools you use when youre programming? For example, the above procedure could easily be accomplished by something like this:

#!/usr/local/bin/bash

[ perl -c "$1" ] &&
cp "$1" "`echo $1| sed 's:.pl::g'`.bak.pl" &&
vim "$1"
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And yeah, you did recently post something on debugging, and I remember upvoting it. After looking in the Secret Search I see:

• RE: debugging
• Re: Are debuggers good?

I'm sure i'm missing stuff.

brother dep.

--
Laziness, Impatience, Hubris, and Generosity.

Yes you are missing something: an OS with a file access subsystem that automatically saves old versions of files for you. My friend you are missing the wonders of VMS :-)

Novell Netware servers used to do that, if I remember correctly. salvage anyone?

Jenda


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