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Postings from February 2022
2022-2-15 11:07 Yuki Kimoto <kimoto.yuki@gmail.com> wrote:
>
> 2022-2-15 10:50 Yuki Kimoto <kimoto.yuki@gmail.com> wrote:
>
>>
>> 2022-2-15 2:12 Paul "LeoNerd" Evans <leonerd@leonerd.org.uk> wrote:
>>
>>>
>>> my ( $minargs, $maxargs ) = builtin::sub_arity $method;
>>> $self->die( "Too few arguments for .$d directive" ) if 1+@args <
>>> $minargs;
>>> $self->die( "Too many arguments for .$d directive" ) if 1+@args >
>>> $minargs;
>>>
>>> return $self->$method( @args );
>>>
>>> Perl currently does not provide this. So I can't.
>>>
>>>
>> If signatures enable arity checking, there is a strong need for the API
>> to get the minimum and maximum number of arguments.
>>
>> This is because generally speaking, module authors know the details of
>> Perl language, but module users don't know the details.
>>
>>
> Additional Description:
>
> In this way, @_ can be suppressed because the definition of a signature is
> determined at compile time;
>
> Callbacks can receive the correct arguments.
>
> $cb->(splice @args, 0, $maxargs);
>
>
>
Additional Description 2:
If arity checking is enabled, and it is included to v5.36
# End user(test.pl)
use v5.36;
use Foo;
Foo->execute(sub ($foo) {
# ...
});
# The module author (This module supports Perl 5.10)
package Foo;
sub execute {
my ($cb) = @_;
$cb->(1);
}
The module author adds an argument after a year.
package Foo;
sub execute {
my ($cb) = @_;
# Adds an argument
$cb->(1, 2);
}
The "test.pl" crashes by the message "Too many arguments". The "test.pl"
maybe a production code.
In order that the module author pass arguments safely, dual life module "
buildin.pm" and the function to pass arguments safely.
# Pass arguments safely
package Foo;
use builtin 'call_cb_safe';
sub execute {
my ($cb) = @_;
# Pass arguments safely
call_cb_safe($cb, (1, 2));
}
The "call_cb_safe" passes the safe arguments to the callback by seeing the
definition of the signatures of the callback.
If the callback doesn't have signatures, all arguments are passed.
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