perl 未初始化值...错误

Question

我在使用严格的代码中不断收到初始化错误，但不明白为什么。我为所有变量设置了正确的范围 - 并且代码运行。只是不明白这些丑陋的错误。

2/15/2002   Joe   155
2/15/2002   Mike  108
2/15/2002   Pete  209
2/22/2002   Joe   158
2/22/2002   Mike  99
2/22/2002   Pete  163
3/1/2002    Joe   172
3/1/2002    Mike  125

#!/usr/bin/perl -w
our %dates;
foreach my $line (<>) {
    chomp $line;
    my ($this_date, $this_name, $this_score) = split /\s+/, $line;
    my ($record_name, $record_score) = split /\|/, $dates{$this_date};
    if ($this_name && $this_score) {
            if ($this_score > $record_score) {
                    $dates{$this_date} = join "|", ($this_name, $this_score);
            }
    }
}

foreach my $date (keys %dates) {
    my ($name, $score ) = split /\|/, $dates{$date};
    print " The high_scored for $date was $name with $score\n";

shortcasper@shortcasper-laptop:~/perl$ ./hash_bowl bowl_linux
Use of uninitialized value in split at ./hash_bowl line 8,  line 7.
Use of uninitialized value $record_score in numeric gt (>) at ./hash_bowl line 10,    line 7.
Use of uninitialized value in split at ./hash_bowl line 8,  line 7.
Use of uninitialized value $record_score in numeric gt (>) at ./hash_bowl line 10,    line 7.
The high_scored for 3/1/2002 was Joe with 172
The high_scored for 2/15/2002 was Pete with 209
shortcasper@shortcasper-laptop:~/perl$

Answer 1

您应该使用警告而不是使用-w。

它抱怨的原因是，当您第一次遇到特定日期时，$dates{$this_date} 是undef（因为它从未被设置过）。拆分会给您一个警告，并使 $record_name 和 $record_score undef （当您比较 $this_score 时，会导致您的第二个警告代码> 到 $record_score）。该代码之所以有效，是因为在数字上，undef 被视为 0，但它会生成警告。

一个简单的解决方法是使用 $dates{$this_date} ||改为“|0”。这为新日期提供了默认值，将 $record_name 设置为空字符串，将 $record_score 设置为 0：

use strict;
use warnings;

our %dates;
foreach my $line (<DATA>) {
    chomp $line;
    my ($this_date, $this_name, $this_score) = split /\s+/, $line;
    my ($record_name, $record_score) = split /\|/, $dates{$this_date} || '|0';
    if ($this_name && $this_score) {
            if ($this_score > $record_score) {
                    $dates{$this_date} = join "|", ($this_name, $this_score);
            }
    }
}

foreach my $date (keys %dates) {
    my ($name, $score ) = split /\|/, $dates{$date};
    print " The high_scored for $date was $name with $score\n";
}

__DATA__
2/15/2002   Joe   155
2/15/2002   Mike  108
2/15/2002   Pete  209
2/22/2002   Joe   158
2/22/2002   Mike  99
2/22/2002   Pete  163
3/1/2002    Joe   172
3/1/2002    Mike  125

但您应该阅读 Perl 数据结构指南 并考虑使用复杂的数据结构，而不必合并和拆分 您的数据只是为了存储它在哈希中。

Answer 2

在我看来，您的哈希 %dates 已初始化，但其值未初始化。您的代码尝试在实际设置之前使用 $dates{$this_date} 的值（这将在几行之后发生）。

Answer 3

%dates 是一个空哈希。所以 $dates{$this_date} 正在变成“undef”

改变你的内在条件，如下所示，使其发挥作用；当没有旧记录时，它将插入日期哈希中。

 if ( !(defined  $record_score) || $this_score > $record_score) {
                $dates{$this_date} = join "|", ($this_name, $this_score);
        }