Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!aplcen!haven!usenet
From: louie@sayshell.umd.edu (Louis A. Mamakos)
Newsgroups: comp.lang.perl
Subject: problems with the defined() function
Message-ID: <1989Dec22.212004.18316@haven.umd.edu>
Date: 22 Dec 89 21:20:04 GMT
Sender: usenet@haven.umd.edu (USENET News Posting)
Organization: The University of Maryland, College Park
Lines: 50

Hello.  I'm having a bit of problem trying to use the defined() function.
What I'm trying to do is call a subroutine whose name is in a variable.  Before
doing such a thing, I'd like to use defined() to tell me if the subroutine
exists or not.

Here's a diddly test program:

#------------------------------------------------
do foo();
&foo();

$bar = "foo";
do $bar();
&$bar();

print "foo is defined\n" if defined(&foo);
print "foo() is defined\n" if defined(&foo());
print "foo via \$bar is defined\n" if defined(&$bar);
print "foo via \$bar() is defined\n" if defined(&$bar());

sub foo {
	print "Hello, in SUB\n";
}
#------------------------------------------------

When I run it, I get:

Hello, in SUB
Hello, in SUB
Hello, in SUB
Hello, in SUB
foo is defined
foo() is defined

Which means that I can invoke the subroutine in 4 different way, which I
expected, but I can't determine if the name of the suboutine exists or not.

Any suggestions?  I'm running the latest version of perl on a NeXT system.
Everything else seems to work ok.

	$Header: perly.c,v 3.0.1.3 89/12/21 20:15:41 lwall Locked $
	Patch level: 8

	Copyright (c) 1989, Larry Wall

	Perl may be copied only under the terms of the GNU General Public License,
	a copy of which can be found with the Perl 3.0 distribution kit.


louie