August 2018
Beginner to intermediate
382 pages
7h 14m
Chinese
Content preview from Perl语言入门
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115
第
6
章
哈希
本章我们会看到
Perl
成为杰出编程语言的关键特色——哈希。尽管哈希非常强大有
用，但那些多年使用其他语言的人却可能从未听说。不过从现在开始，几乎每个
Perl
程序中你都会用到哈希。是的，它真的非常重要。
什么是哈希？
哈希是一种数据结构，它和数组的相似之处在于可以容纳任意多的值，并可按需取
用，而它和数组的不同之处在于检索方式不同，数组是以数字下标来检索，哈希则以
唯一的名字来检索。我们把这个唯一的名字称为键（
key
）（参阅图
6-1
）。
哈希的键只能使用普通的字符串表示。类似于通过数字
3
获取数组元素，我们可以
用
wilma
这个名字来存取哈希元素。
这些键可以是任何字符串——你可以用任意字符串表达式作为哈希键。它们也必须
是唯一的字符串，就像数组只能有一个编号为
3
的元素一样，哈希也只能有一个名
叫
wilma
的元素。
我们可以把哈希想象成一大桶数据，其中每个数据都有关联的标签。你可以伸手到桶
里任意取出一张标签，看它上面写的数据是什么。但是桶里没有“第一个”元素，只
有一堆元素。在数组里，第一个为元素
0
，然后是元素
1
、
2
等等，但哈希里没有顺
序，因此也没有所谓的第一个元素，有的只是一堆键
-
值对的集合。
116
｜
第
6
章
图
6
-
1
：哈希的键与值
这些键和值都是任意的标量，但键总会被转换成字符串。假如你以数字表达 ...
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