使用 Perl6 散列键定义与存在 [英] Defined vs. exists with Perl6 hash keys

问题描述

我正在从 Perl5 学习 Perl6.

I am learning Perl6 from Perl5.

我在看副词 :exists https://docs.perl6.org/type/Hash#:exists 但没有 :defined 副词

I am looking at the adverb :exists https://docs.perl6.org/type/Hash#:exists but there isn't a :defined adverb

但我很担心，因为 perl5 的 exists &defined:存在和定义有什么区别?

but I am concerned because there is a distinction between perl5's exists & defined: What's the difference between exists and defined?

我怎样才能在 Perl6 中做这样的事情?

How can I do something like this in Perl6?

if (defined $hash{key}) {
   $hash{key}++;
} else {
   $hash{key} = 1;
}

推荐答案

if defined %hash{'key'} {
   %hash{'key'}++;
} else {
   %hash{'key'} = 1;
}

使用 defined 例程或方法.请参阅 5to6-perlfunc -- 已定义

Use the defined routine or method. See 5to6-perlfunc -- defined

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