perl exist函数_Perl快速教程exist（）函数

比眉伴天荒 2022-12-06 15:37 1阅读 0赞

perl exist函数

Perl's **exists()** function is used to check whether an element in an [array][] or [hash][] exists. It can also be used to check for the existence of subroutines. **exists** will return true as long as the element has been initialized, and even if the element is undefined.

Perl的**exist()**函数用于检查[数组][array]或[哈希中][hash]的元素是否存在。 它也可以用来检查子程序的存在。 只要元素已初始化，即使元素未定义，则**存在**将返回true。

In the above example, we look at a **hash** of our contact Bob and his phone number. First, we check for the existence of the **phone** element, which is obviously returning **true**. Next, we check for an element that does not exist, **address**, and you'll see this one returns **false**.Let's look at the same routine, but with a blank **address** key:

在上面的示例中，我们查看了联系人Bob和他的电话号码的**哈希**值。 首先，我们检查**phone**元素是否存在，显然返回**true** 。 接下来，我们检查一个不存在的元素**address** ，您将看到这个返回**false** 。让我们看一下相同的例程，但是有一个空白的**address**键：

You'll see that this one returns true on the address, even though there is no actual value. Be careful relying on the logic of **exists**, and remember the distinction between **exists** and **has value**.

您会看到，即使没有实际值，该地址也将返回true。 要小心依靠**存在**的逻辑，并记住**存在**与**具有价值**的区别。

> 翻译自: [https://www.thoughtco.com/perl-exists-function-quick-tutorial-2641184][https_www.thoughtco.com_perl-exists-function-quick-tutorial-2641184]

perl exist函数

[array]: https://www.thoughtco.com/how-to-create-arrays-in-ruby-2908192
[hash]: https://www.thoughtco.com/how-to-create-hashes-2908196
[https_www.thoughtco.com_perl-exists-function-quick-tutorial-2641184]: https://www.thoughtco.com/perl-exists-function-quick-tutorial-2641184