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Prototypes suffer from several other problems, too. They can change function behavior, by forcing scalar context when evaluating arguments that might not be scalars, or by forcing list context when evaluating arguments that might not be lists. Prototypes do not affect functions defined using the A function's prototype is ignored when that function is invoked with the & character. Finally, according to the perlfunc manpage [Wall 2011]:
Method calls are not influenced by prototypes either, because the function to be called is indeterminate at compile time, since the exact code called depends on inheritance.
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| Code Block | ||||
|---|---|---|---|---|
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sub function ($@) {
my ($item, @list) = @_;
print "item is $item\n";
my $size = $#list + 1;
print "List has $size elements\n";
foreach my $element (@list) {
print "list contains $element\n";
}
}
my @elements = ("Tom", "Dick", "Harry");
function( @elements);
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However, this program generates the following counterintuitive output:
| Code Block |
|---|
item is 3 List has 0 elements |
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| Code Block | ||||
|---|---|---|---|---|
| ||||
sub function {
my ($item, @list) = @_;
print "item is $item\n";
my $size = $#list + 1;
print "List has $size elements\n";
foreach my $element (@list) {
print "list contains $element\n";
}
}
my @elements = ("Tom", "Dick", "Harry");
function( @elements);
|
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| [Conway 2005] | "Prototypes," p. 194 |
| [CPAN] | Elliot Shank, Perl-Critic-1.116 Subroutines::ProhibitSubroutinePrototypes |
| [Wall 2011] | perlsub |
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