在Perl中,当我尝试初始化哈希时,为什么我会在"偶数大小列表预期"中找到"引用"？

Question

我有一个脚本作为输入两个文件:

• 提取200k行
• 源文件

我必须将提取与源进行比较:提取的每一行都应该在源中.如果没有,我必须记录一行日志文件.

脚本下方:

#!/perl/bin/perl
use strict;
use warnings;
use feature 'say';
# Open log file
open(LOG, '>', 'log.txt');
# Start log
say LOG '['.localtime().'] Début execution';
# Declare extraction number of line counter
my $i_extraction_counter = 1;
# Define files to be compared (extraction against source)
my ($extraction_file, $source_file) = @ARGV;
# Open extraction file
open my $f_extraction, "<", $extraction_file;
# Store extraction file in a hash
my %h_extraction;
while(defined(my $extr_line = <$f_extraction>)){
    $h_extraction{$extr_line} = $extr_line;
    $i_extraction_counter++;
}
# Declare temp hash and counter
my %h_tmp = {};
my $i_counter = 1;
# Open source file
open my $f_source, "<", $source_file;
# For each source line, compare against extraction hash
while(defined(my $source_line = <$f_source>)){
    # If the current line exists in extration hash, stores it in the temp hash & increase counter
    if(defined($h_extraction{$source_line})){
        $h_tmp{$source_line} = $source_line;
        $i_counter++;
    }
    # TO DO : check in elsif if the line should be stored in log (name + firstname OR contract number)
}
# If not all lines of extraction has been stored in temp hash = some lines of extraction are not in source file
if($i_counter < $i_extraction_counter){
    # Declare a second temp hash (used to log missing lines)
    my %h_missing_lines = %h_extraction;
    # For each line of extraction, check if it exists in the first temp hash. If yes, unset it. Only missing line will remain
    foreach my $s_line (keys(%h_missing_lines)){
        if(defined($h_tmp{$s_line})){
            delete($h_missing_lines{$s_line});
        }
    }
    # For each line of missing lines hash, stores it in log file
    foreach my $s_line (keys(%h_missing_lines)){
        say LOG 'Ligne d\'extraction non présente dans fichier source : '.$s_line;
    }
}
say LOG '['.localtime().'] Fin execution';

在执行时,此消息显示: Reference found where even-sized list expected at script.pl line 22, <$f_extraction> line 200000.

Answer 1

在第22行,我们有:

my %h_tmp = {};

改为:

my %h_tmp;

你会没事的.

这里的问题是 - {}用于定义匿名哈希 - 并返回引用.

所以你可以这样做:

my $hash_ref = {}; 

而这正是你正在做的事情.

my %h_tmp = $hash_ref; 

使用像这样的单个值初始化散列,可以准确地给出您所获得的错误,因为散列需要键值对.

你可以这样做:

my %h_tmp = (); 

这可以工作,但是会多余 - 你无论如何都要创建一个空哈希.