Re: USAGE OF Prototype

prototypes can act as a check on the code to ascertain that function calls are performed properly, they indicate to Perl:

Types of arguments the function can take.
the number of arguments intended to be passed to the function.

(updated)

prototypes are flexible, you can also indicate to a function whether a certain prototype is optional and you can include references to hashes in there.

example:
sub NAME($$;$){...}  #mistake corrected
[download]

this function expects 2 scalar arguments and one optional argument after the ";"...so bear in mind that not all of this is irrelevant and there will come a time when you'd better use a prototype in a function definition than pass it over.

Excellence is an Endeavor of Persistence. Chance Favors a Prepared Mind.

Comment on Re: USAGE OF Prototype Download Code

Replies are listed 'Best First'.
Re^2: USAGE OF Prototype by SuicideJunkie (Vicar) on Aug 06, 2009 at 15:36 UTC
How would you go about inspecting the contents of a scalar to decide if it is a number using only prototypes? That sounds like more of a job for: `confess("Parameter $n stinks") unless $param[$n] =~ /$goodRule[$n]/;` [download] Append: Example of extensive parameter handling: sub buyWidgets { my $numWidgets = shift; my $supplier = shift; #validate parameters unless ($numWidgets =~ /^\d+$/) { carp("'$numWidgets' is not a valid number of widgets: purchase + canceled\n"; return undef; } # Validate, and be flexible if possible. Accept both "ACME" and +"hash(0xPtrToACME)", and even ["ACME", "Bob's Widgets", "Black Market +"] if (ref($supplier) eq 'ARRAY') { my $buyCount = 0; foreach (@$supplier) { my $result = buyWidgets($numWidgets-$buyCount, $_); $buyCount += $result if defined($result); } return $buyCount; } if (ref($supplier) ne 'Supplier') { unless (exists $globalSupplierDirectory->{$supplier}) { carp("Cannot buy from '$supplier': not a valid supplier\n" +); return undef; } $supplier = $globalSupplierDirectory->{$supplier}; } # Do stuff with the good parameters return $supplier->buyWidgets($numWidgets); } [download] Untested, and not self-contained.	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re^2: USAGE OF Prototype
by SuicideJunkie (Vicar) on Aug 06, 2009 at 15:36 UTC

confess("Parameter $n stinks") unless $param[$n] =~ /$goodRule[$n]/;
[download]

sub buyWidgets
{
    my $numWidgets = shift;
    my $supplier = shift;
    
    #validate parameters
    unless ($numWidgets =~ /^\d+$/)
    {
        carp("'$numWidgets' is not a valid number of widgets: purchase
+ canceled\n";
        return undef; 
    }
   
    # Validate, and be flexible if possible.   Accept both "ACME" and 
+"hash(0xPtrToACME)", and even ["ACME", "Bob's Widgets", "Black Market
+"]
    if (ref($supplier) eq 'ARRAY')
    {
        my $buyCount = 0;
        foreach (@$supplier)
        {
            my $result = buyWidgets($numWidgets-$buyCount, $_);
            $buyCount += $result if defined($result);
        }
        return $buyCount;
    }
    if (ref($supplier) ne 'Supplier')
    {
        unless (exists $globalSupplierDirectory->{$supplier})
        {
            carp("Cannot buy from '$supplier': not a valid supplier\n"
+);
            return undef;
        }
        $supplier = $globalSupplierDirectory->{$supplier};
    }

    # Do stuff with the good parameters
    return $supplier->buyWidgets($numWidgets);
}
[download]

[reply]
[d/l]
[select]