Question

我认为我有正确的想法，但有一些语法/惯例我搞砸了，因为我收到错误“全局符号％timeHash需要显式包名称。”

代码：

foreach $key (sort hashValueDescendingNum (keys(%timeHash))) {
   print "\t$key\t\t $timeHash{$key}\n";
}



sub hashValueDescendingNum {
   my $hash = shift;
   $hash{$b} <=> $hash{$a};
}

Answer 1

内联

foreach my $key (sort { $timeHash{$b} <=> $timeHash{$a} } keys %timeHash) {
   print "\t$key\t\t $timeHash{$key}\n";
}

使用自定义排序功能，您尝试的方式将无法正常工作，因为您的sub需要访问原始哈希。

foreach my $key (sort hashValueDescendingNum (keys(%timeHash))) {
    print "\t$key\t\t $timeHash{$key}\n";
}

sub hashValueDescendingNum {
   $timeHash{$b} <=> $timeHash{$a}; # Ew.
}

相反，你可以进一步抽象它：

foreach my $key (sortedHashKeysByValueDescending(%timeHash)) {
    print "\t$key\t\t $timeHash{$key}\n";
}

sub sortedHashKeysByValueDescending {
  my %hash = @_;
  my @keys = sort { $hash{$b} <=> $hash{$a} } keys %hash;
  return @keys;
}

代码效率不高，因为它传递％hash，但引用会更好：

foreach my $key (sortedHashKeysByValueDescending(\%timeHash)) {
    print "\t$key\t\t $timeHash{$key}\n";
}

sub sortedHashKeysByValueDescending {
  my $hash = shift;
  return sort { $hash->{$b} <=> $hash->{$a} } keys %$hash;
}

Answer 2

use List::UtilsBy qw( rev_nsort_by );

foreach my $key ( rev_nsort_by { $timeHash{$_} } keys %timeHash ) {
    ...
}

Perl按散列中的值排序哈希值

2 个答案: