in reply to test for subroutine existence

To see whether something is defined, you use the defined function: 
#!/usr/bin/perl

use warnings 'all';
use strict;

sub my_sub {1}

print "my_sub ", defined &my_sub ? "exists\n" : "doesn't exist\n";
print "no_sub ", defined &no_sub ? "exists\n" : "doesn't exist\n";

__END__
my_sub exists
no_sub doesn't exist

[download]
Abigail

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Re: Re: test for subroutine existence
by twerq (Deacon) on Aug 12, 2002 at 14:20 UTC
    Sorry, I probably wasn't clear enough in my original post (but that's why I added the code)...
    I need to be able to test for a subroutine's existence, a subroutine who'se name is only available to me in a scalar -- so I can't very well use defined &my_sub (or can I?)

    fuzzyping's right, eval does work pretty well, except that I end up actually executing the subroutine itself just to see if it's there -- I'd prefer not to actually run it at test time...

    --twerq
[reply]
[d/l]
      No eval needed. 
      #!/usr/bin/perl

use warnings 'all';
use strict;

sub my_sub {1}

foreach my $sub (qw /my_sub no_sub/) {
    print "$sub ", defined &$sub ? "exists\n" : "doesn't exist\n";
}

__END__
my_sub exists
no_sub doesn't exist

      [download]
      Abigail
[reply]
[d/l]
      Okay, anyway -- now it seems pretty obvious:
      print "my_sub ", test_for_sub("my_sub") ? "exists\n" : "doesn't exist\
+n";
print "no_sub ", test_for_sub("no_sub") ? "exists\n" : "doesn't exist\
+n";

sub test_for_sub {
        my ($expr) = @_;
        return eval "defined &$expr";
}

sub my_sub { 1; }

      [download]


      --twerq
[reply]
[d/l]

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