October 2022
Beginner to intermediate
390 pages
7h 5m
Chinese
Content preview from Perl语言入门（第8版）
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60
｜
第
3
章
如果数组是空的，
pop
什么也不做（因为没有任何元素可供移出），直接返
回
undef
。
你也许已经注意到了，
pop
后面加不加括号都可以。这是
Perl
的惯例之一：只要拿掉
括号不会改变原意，括号就可省略。与其对应的是
push
操作符，用于添加一个元素
（或是一串元素）到数组末尾：
push(@array, 0); # @array
现在是
(5, 6, 0)
push @array, 8; # @array
现在是
(5, 6, 0, 8)
push @array, 1..10; # @array
得到了
10
个新元素
@others = qw/ 9 0 2 1 0 /;
push @array, @others; # @array
又得到了
5
个新元素（共
19
个）
注意，
push
的第一个参数或者
pop
的唯一参数必须是要操作的数组变量——对列表
直接量进行压入（
push
）或弹出（
pop
）操作是没有意义的。
shift
和
unshift
操作符
push
和
pop
操作符处理的是数组的末尾（或者说数组的“右”边，最高下标值的部
分，怎么理解都行）；相似地，
unshift
和
shift
操作符则是对数组的“开头”（或
者说数组的“左”边，最低下标值的部分）进行相应的处理。来看几个例子：
@array = qw# dino fred barney #;
$m = shift(@array); # $m
变成
"dino", @array
现在是
("fred", ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.