subroutine introspection

misterb101 has asked for the wisdom of the Perl Monks concerning the following question:

Hi fellow Perl mates, I am working on a big application using ExtJS as a front-end. The interface communicates with the backend using Ext::Direct, a JSON API. What I am trying to do is create the API specification automatically. The API basically requires 2 things. specify which subroutines are made accessible and how many parameters they take, which I am solving like this:

sub foo($$) : Direct {
    ...
}
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The subroutine attribute is not a problem, but I can't seem to figure out how I can list how many arguments the subroutine requires:

my $numArgs = GiveMeTheNumberOfRequiredArgumentsOf(\&foo);
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can anyone implement the 'GiveMeTheNumberOfRequiredArgumentsOf' subroutine for me ;) ? THANKS

--
Cheers,
Rob

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Re: subroutine introspection by JavaFan (Canon) on Dec 22, 2010 at 16:32 UTC
You can get the prototype of a function as: `prototype \&foo;` [download] I leave it up to you to parse the prototype (which has been enhanced in recent Perl versions).	[reply] [d/l]
Re^2: subroutine introspection by misterb101 (Sexton) on Dec 22, 2010 at 19:29 UTC
I have been programming Perl for 15 years... and I never knew this amazingly simple function.... Thanks for enlightening me :D -- Cheers, Rob	[reply]
Re: subroutine introspection by ikegami (Patriarch) on Dec 22, 2010 at 17:32 UTC
Do you want the minimum number of arguments that must be specified, or the miminum number of arguments that must be passed to the function? `# Minimum number of arguments that must be specified = 0 # Miminum number of arguments that must be passed = 1 sub f(_) {}` [download] `# Minimum number of arguments that must be specified sub get_min_require_params { my ($sub) = @_; my $required_params = 0; my $prototype = prototype($sub); return 0 if !defined($prototype); for ($prototype) { if (/ \G (?: \$ \| \* \| \\(?: \[ [^\]] \] \| [^\[] ) \| \& ) /xsgc) { ++$required_params; next; } if (/ \G (?: \_ # Can only be followed by ";" \| \@ \| \% \| \; \| \z /xsgc) { last; } die("Unrecognized prototype\n"); } }` [download] To get the minimum number of arguments that must be passed to the function, you'll need to move "_" to the top "if". I don't see how either version is useful, so I'm sure there's an XY problem lurking. perlsub (for info on prototypes), prototype	[reply] [d/l] [select]