Perl子例程从何处获取实际参数中缺少的值？_Perl_Optional Parameters_Subroutine

Perl子例程从何处获取实际参数中缺少的值？

perl

Perl子例程从何处获取实际参数中缺少的值？,perl,optional-parameters,subroutine,Perl,Optional Parameters,Subroutine,在跟踪一个bug时，我遇到了以下Perl子例程get\u billable\u pages。它需要12个参数 sub get_billable_pages { my ($dbc, $bill_pages, $page_count, $cover_page_count, $domain_det_page, $bill_cover_page, $virtual_page_billing, $job,

在跟踪一个bug时，我遇到了以下Perl子例程

get\u billable\u pages

。它需要12个参数

sub get_billable_pages {
    my ($dbc,
        $bill_pages,      $page_count,      $cover_page_count,
        $domain_det_page, $bill_cover_page, $virtual_page_billing,
        $job,             $bsj,             $xqn,
        $direction,       $attempt,
    ) = @_;

    my $billable_pages = 0;

    if ($virtual_page_billing) {
        my @row;
        ### Below is testing on the existence of the 11th and 12th parameters ###
        if ( length($direction) && length($attempt) ) {
            $dbc->xdb_execute("
                SELECT convert(int, value)
                FROM   job_attribute_detail_atmp_tbl
                WHERE  job             = $job
                AND    billing_sub_job = $bsj
                AND    xqn             = $xqn
                AND    direction       = '$direction'
                AND    attempt         = $attempt
                AND    attribute       = 1
            ");
        }
        else {
            $dbc->xdb_execute("
                SELECT convert(int, value)
                FROM job_attribute_detail_tbl
                WHERE job             = $job
                AND   billing_sub_job = $bsj
                AND   xqn             = $xqn
                AND   attribute       = 1
            ");
        }
        $cnt = 0;
        ...;

但有时只调用10个参数

$tmp_det = get_billable_pages(
    $dbc2,
    $row[6],          $row[8],          $row[7],
    $domain_det_page, $bill_cover_page, $virtual_page_billing,
    $job1,            $bsj1,            $row[3],
);

函数对第11个和第12个参数进行检查

sub get_billable_pages {
    my ($dbc,
        $bill_pages,      $page_count,      $cover_page_count,
        $domain_det_page, $bill_cover_page, $virtual_page_billing,
        $job,             $bsj,             $xqn,
        $direction,       $attempt,
    ) = @_;

    my $billable_pages = 0;

    if ($virtual_page_billing) {
        my @row;
        ### Below is testing on the existence of the 11th and 12th parameters ###
        if ( length($direction) && length($attempt) ) {
            $dbc->xdb_execute("
                SELECT convert(int, value)
                FROM   job_attribute_detail_atmp_tbl
                WHERE  job             = $job
                AND    billing_sub_job = $bsj
                AND    xqn             = $xqn
                AND    direction       = '$direction'
                AND    attempt         = $attempt
                AND    attribute       = 1
            ");
        }
        else {
            $dbc->xdb_execute("
                SELECT convert(int, value)
                FROM job_attribute_detail_tbl
                WHERE job             = $job
                AND   billing_sub_job = $bsj
                AND   xqn             = $xqn
                AND   attribute       = 1
            ");
        }
        $cnt = 0;
        ...;

当函数只传递10个参数时，第11个和第12个参数是什么
因为第11个和第12个参数都是随机值，所以只使用10个参数调用函数是错误的吗
我认为这可能是错误的根源，因为当程序失败时，第12个参数有一个古怪的值
我没有看到函数的另一个定义，它只接受10个参数

sub foo {
    my ($x, $y) = @_;
    print " x is undef\n" unless defined $x;
    print " y is undef\n" unless defined $y;

}

foo(1);

 y is undef

undef

ikegami

use strict;
use warnings;

use Data::Dumper;

my $x = 44;             # Make sure that we
my $y = 55;             # know if they change

my @params = (8);       # Make a dummy parameter array with only one value

($x, $y) = @params;     # Copy as if this is were a subroutine

print Dumper $x, $y;    # Let's see our parameters
print Dumper \@params;  # And how the parameter array looks

输出

$VAR1 = 8;
$VAR2 = undef;

$VAR1 = [ 8 ];

$x

$y

undef

unde

if ( length($direction) && length($attempt) ) { ... }

使用警告

使用未初始化值

length

undef

undef

关于“我没有看到函数的另一个定义，只需要10个参数”，Perl没有像C++和java那样的函数模板——它是在子程序中的代码来查看它已经通过的和相应的行为。< /P>这只是列表分配的标准行为；函数参数并没有什么特别之处。我正要说“Borodin很快会告诉您使用警告和严格限制”。他几乎肯定没有穿，因为un my'd

$cnt=0

length undef

undef