Re: Any difference between use and require regarding honoring prototype defined for sub? (prototype)

Yes, there is a difference, use use and not require

should be documented in perlsub

if you use require, you'll need to use a forward declaration

$ perl -le "sub f($$@@){warn qq{@_}} f(@ARGV,@ARGV,@ARGV); " 1 2 3 4 5
5 5 1 2 3 4 5 at -e line 1.

## simulate "require"
$ perl -le " eval q{sub f($$@@){warn qq{@_}}}; f(@ARGV,@ARGV,@ARGV); "
+ 1 2 3 4 5
1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 at (eval 1) line 1.

## forward/early/prototype declaration
$ perl -le " sub f($$@@); eval q{sub f($$@@){warn qq{@_}}}; f(@ARGV,@A
+RGV,@ARGV); " 1 2 3 4 5
5 5 1 2 3 4 5 at (eval 1) line 1.
[download]

$ echo foo() called too early to check prototype at file line 12 |spla
+in
foo() called too early to check prototype at file line 12  (#1)
    (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 a
+n
    early prototype declaration for the subroutine in question, or mov
+e the
    subroutine definition ahead of the call to get proper prototype
    checking.  Alternatively, if you are certain that you're calling t
+he
    function correctly, you may put an ampersand before the name to av
+oid
    the warning.  See perlsub.
[download]

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Re^2: Any difference between use and require regarding honoring prototype defined for sub? (prototype) by stewart_lee (Novice) on Nov 19, 2012 at 19:56 UTC
Thanks, what I read the difference between use and require is that module included by use is loaded in compilation while it is loaded in execution by require, but they won't cause any difference on hornoring the protocol defined for the sub. But in my example, if I use 'use', then I should call the sub with ($$@@) instead of ($$\@\@) as defined for sub's protocol. Also, when trying your 3 commands, only the second one seems good. `$ perl -le "sub f($$@@){warn qq{@_}}; f(@ARGV,@ARGV,@ARGV); " 1 2 3 4 +5 Malformed prototype for main::f: 29673@@ at -e line 1. $ perl -le " eval q{sub f($$@@){warn qq{@_}}}; f(@ARGV,@ARGV,@ARGV); " + 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 1 2 3 4 5 at (eval 1) line 1. $ perl -le " sub f($$@@); eval q{sub f($$@@){warn qq{@_}}}; f(@ARGV,@A +RGV,@ARGV); " 1 2 3 4 5 Malformed prototype for main::f: 29673@@ at -e line 1.` [download]	[reply] [d/l]
Re^3: Any difference between use and require regarding honoring prototype defined for sub? by Athanasius (Archbishop) on Nov 20, 2012 at 04:50 UTC
Hello stewart_lee, and welcome to the Monastery! I use 'use', then I should call the sub with ($$@@) instead of ($$\@\@) I think you may be confused about how prototypes work in Perl. Specifically, `($$\@\@)` means the subroutine expects: a scalar another scalar an array (not an array reference!) another array The backslash in the prototype — `\@` — means the array will be converted into an array reference inside the sub. So, in your example, `Money::Finance::getMovingAve(5,$size,@values,@mv); ... sub getMovingAve($$\@\@) { my ($count, $number, $values, $movingAve) = @_; ...` [download] the variables `$values` and `$movingAve` are assigned references to the arrays `@values` and `@mv`, respectively, by virtue of the subroutine’s prototype. So, with use, the code is behaving as expected. But with require, the prototype is ignored because it is seen too late, so to make the sub work correctly you have to pass references explicitly. Perl prototypes are confusing, and should probably be avoided unless you have a good reason to use them. Make sure to read Far More than Everything You've Ever Wanted to Know about Prototypes in Perl -- by Tom Christiansen. By the way, you would probably have received help sooner had you posted a trimmed-down (but still working) version of the code showing only the relevant parts. See How do I post a question effectively? And do not comment out `use strict;` — it’s there to make your life easier! Hope that helps, Athanasius <°(((>< contra mundum	[reply] [d/l]
Re^2: Any difference between use and require regarding honoring prototype defined for sub? (prototype) by stewart_lee (Novice) on Nov 21, 2012 at 17:27 UTC
Thank you Athanasius, I got it.	[reply]