在Perl中切片嵌套的哈希 [英] Slicing a nested hash in Perl

问题描述

说我有一个哈希，我可以将其索引为:

Say I have a hash that I can index as:

$hash{$document}{$word}

从我在网上阅读的内容(尽管我在 perlreftut ， perldsc 或

From what I read online (although I could not find this on perlreftut, perldsc or perllol), I can slice a hash using a list if I use the @ prefix on my hash to indicate that I want the hash to return a list. However, if I try to slice my hash using a list @list:

@%hash{$document}{@list}

我遇到几个"Scalar values ... better written"错误.

如何在Perl中削减嵌套的哈希?

How can I slash a nested hash in Perl?

推荐答案

您的哈希的签名必须为@，如下所示:

The sigill for your hash must be @, like so:

@{$hash{$document}}{@list}

假定@list包含%hash的有效键，它将返回相应的值；如果键不存在，则返回undef.

Assuming @list contains valid keys for %hash it will return the corresponding values, or undef if the key does not exist.

这是基于哈希切片的一般规则:

This is based on the general rule of a hash slice:

%foo = ( a => 1, b => 2, c => 3 );
print @foo{'a','b'};               # prints 12
%bar = ( foo => \%foo );           # foo is now a reference in %bar
print @{ $bar{foo} }{'a','b'};     # prints 12, same data as before

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