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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标量数据
｜
37
对数字进行运算的操作符（比如乘法）如果遇到字符串类型的操作数，
Perl
会自动将
字符串转换成等效的十进制浮点数进行运算。因此
"12" * "3"
的结果会是
36
。字符
串中非数字的部分（以及前置的空白符号）会被略过，所以
"12fred34" * "3"
也会得
出
36
，而不会出现任何警告信息（除非你要求
Perl
显示警告信息，稍后我们就会提
到有关警告信息的处理）。完全不含数字的字符串会被转换成零，比如把
"fred"
当
成数字来用，就是这种情况。
前导
0
的技巧只能用于八进制直接量，不能用于字符串的自动转换。请记住，自动转
换总是基于十进制数字来处理的：
0377 #
十进制数字
255
的八进制写法
'0377' #
会转换成十进制数字
377
稍后我们会介绍
oct
的用法，将字符串转换为八进制数字。
同样地，处理字符串的操作符（比如字符串连接操作符）如果得到的是数字的话，该
数字就会被转换为形式相同的字符串。比如要把字符串
Z
与“
5
乘以
7
的结果”相连
接，写起来非常简单：
"Z" . 5 * 7 #
等同于
"Z" . 35
，得
"Z35"
基本上你不用关心数字和字符串的差别（大多数时候），
Perl
会自动完成数据转换的
工作。并且更进一步地，
Perl
会记住已完成的转换，以便重复计算时不再浪费时间，
更快得到结果。
Perl
的内置警告信息
当
Perl
发现程序代码中有可疑之处时，可以通过警告信息提示你。从
Perl 5.6
开始，
我们可以通过编译指令启用警告机制（请注意查看所用的版本是否支持）： ...
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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.