Re: Calling Functions

So I found that if I change the code to the following I no longer get the warning,

#!/usr/bin/perl

use strict;
use warnings;

sub test2() {
    print "test2: Working\n";
}

print "About to test sub calls using \& --\n";
&test1;

print "About to test sub call using name() --\n";
test2();

sub test1() {
    print "test1: Working\n";
}
[download]

So I have to declare the function before I call it.

"(W prototype) You've called a function that has a prototype before the parser saw a definition or declaration for it, and Perl could not check that the call conforms to the prototype. You need to either add an early prototype declaration for the subroutine in question, or move the subroutine definition ahead of the call to get proper prototype checking. Alternatively, if you are certain that you're calling the function correctly, you may put an ampersand before the name to avoid the warning."

So I guess that answers Question 1. Thanks Perlmonks!

I guess the comment in italics also explains the use of the & then.

Bah!! I also added use diagnostics; and got the above mentioned paragraph.. it also told me to read perlsub

So I guess that answers 3 of the 4 questions and I bet that reading perlsub I'll clearly see the reasons you need &subname as apposed to subname()

Sorry for posting this too quickly!

Of all the things I've lost in my life, its my mind I miss the most.

Comment on Re: Calling Functions Select or Download Code

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Re^2: Calling Functions by GrandFather (Saint) on Mar 28, 2012 at 08:39 UTC
Well done! No, you didn't post too quickly and you gain kudos for posting a follow up with the stuff you found and figured out. Once again: well done! The perlsub (I recommend the more up to date perldoc.org link btw) is indeed the place to go for the god oil on this matter, although some of the subtle traps are not really highlighted. As you found calling using & ignores prototypes. However as prototypes should almost never be used that is not a big issue. The more subtle potential trap is that the current contents of @_ is used as the argument list to the called subroutine if no explicit arguments are provided. True laziness is hard work	[reply]
Re^2: Calling Functions by eclpmb (Hermit) on Mar 28, 2012 at 08:31 UTC
The main thing is that you're using prototypes. Generally prototypes aren't needed, aren't used and can be harmful unless you're very careful. If you define test2 as `sub test2 { print "test2: Working\n"; }` [download] you'll find you're able to call it before it's defined, without getting a warning.	[reply] [d/l]


Think about Loose Coupling
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