Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!unmvax!uokmax!d.cs.okstate.edu!drd!mark
From: mark@DRD.Com (Mark Lawrence)
Newsgroups: comp.lang.perl
Subject: Proper Use of Packages and Debugging With Same
Summary: do 'foo.pl'; do foo'bar($bar, $gex, $snark);
Keywords: packages debugging
Message-ID: <1990Jul12.143602.23401@DRD.Com>
Date: 12 Jul 90 14:36:02 GMT
Reply-To: mark@drd.Com (Mark Lawrence)
Organization: DRD Corporation, Tulsa, OK
Lines: 54

The subject line says it all -- I want to use packages in the way they
were intended and I'd like to be able to use the debugger in a script
that uses packages.

I admit that my concept of how packages were intended to be used may be
bogus.  The man page says they give a local namespace to the enclosing
block so as not to conflict with namespaces of callers (hence, safe
re-useability).  As an added bonus, they can be put into separate files
that other scripts can 'do' (to get the code interpreted in) so that
common subs can be made generally available.

So, I write myself a few packages to perform operations common to a
number of scripts: foo.pl, bar.pl and gex.pl

foo.pl:              bar.pl:               gex.pl:
package foo;         package bar;          package gex;
sub foo'DoThis {     sub bar'Snicker{      sub main'gex{
...                  ...                   ...
}                    }                     }
                     sub bar'Snort{
					 ...
					 }

In an example script, towards the top, I say:

do 'gex.pl'; do 'bar.pl'; do 'foo.pl';

and then when I want to call one of the functions, I say:

do main'gex(args); do bar'Snort(args); # and so forth

(The `main' qualifier in gex.pl, BTW, is there on purpose: we actually have
a package that does this, because of the example with package dumpvar in the 
Packages section of the man page.  Why use a package if you're not going
to take advantage of the alternative namespace?  Or am I really
confused?)

When I fire the script up in the debug mode, I say:
c ## where the line number is past the do 'file' type of calls and past
one of the lines in which we actually call a sub defined in a function
and I get:

Undefined subroutine "Snort" called at Script.pl line ## ...

I guess it makes sense to me that Snort is an undefined symbol in the
`main' namespace, but shouldn't the debugger handle that (especially
since in code I qualify it properly?)  How do I debug this so that I can
'step' into packages and watch them execute?  Now, I just read the
package into my file, comment out the package lines and remove the
qualifiers and then test the script as if all subs were 'local', as it
were.  Isn't there a better way?
-- 
mark@DRD.Com uunet!apctrc!drd!mark$B!J%^!<%/!!!&%m!<%l%s%9!K(B
 "...do justice, love mercy, and walk humbly..." Micah 6:8