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
｜
31
要知道，逗号在
Perl
里还有更加重要的作用（请阅读第
3
章），所以为了避免歧义，
我们改用下划线。再说了，也不是所有国家和地区都用逗号分隔千位的。
非十进制整数的直接量
和许多其他编程语言一样，除了十进制（
decimal
，基数为
10
）以外，
Perl
也可以用其
他进制来表示数字直接量。八进制（
octal
，基数为
8
）直接量以
0
开头，后跟数字
0
到
7:
0377 #
等于十进制的
255
从
v5.34
开始，还可以用
0o
作为八进制数的前导标志，这使八进制数与你将要看到的
其他基数保持一致：
0o377 #
等于十进制的
255
十六进制（
hexadecimal
，基数为
16
）直接量以
0x
开头，后跟数字
0
到
9
以及字
母
A
到
F
（或者小写字母
a
到
f
）表示十进制中
0
到
15
的值：
0xff #
或者用大写
FF
，也等于十进制的
255
二进制（
binary
，基数为
2
）直接量以
0b
开头，后跟数字
0
或
1
：
0b11111111 #
等于十进制的
255
虽然这三个数字的写法不同，但对
Perl
来说都是同一个数字。所以写成
0377
也好，
写成
0xFF
也罢，都表示数字
255
。选择哪种书写形式，取决于参与运算的需要。例如
许多
Unix
系统中的
shell
命令惯用八进制数字，所以在第
12
章和第
13
章会看到
Perl
里面八进制数字形式的示例。
前导
0
的写法只用于表示数字直接量，不能用于字符串和数字间的自动转换。 ...
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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.