January 2021
Intermediate to advanced
505 pages
9h 45m
Chinese
Content preview from PHP编程：第4版
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数据类型
｜
23
幸的是，
C
标准并没有指定
long
数据类型的具体范围，所以在一些系统里会有不同的整
型范围。
整型字面量可以用十进制数、八进制数、二进制数或十六进制数表示。十进制数由不以
0
开头的数字序列表示。这个数列可以用正号（
+
）或 负 号（
-
）开头。如果开头没有符号，
就假定为正数。下面是包含了一些十进制整型数的例子 ：
1998
-
641
+33
八进制数由一个前导
0
和一个从
0
到
7
的数字序列组成。和十进制数一样，八进制数可
以用正号或负号作为前缀。下面是一些八进制数及与它们等值的十进制数的例子 ：
0755 //
十进制数
493
+010 //
十进制数
8
十六进制数是以
0x
开头的数字（
0
～
9
）或 字 母（
A
～
F
）的序列。字母可以是大写或小写，
但通常是大写。同十进制数和八进制数一样，十六进制数也可以包含符号 ：
0xFF //
十进制数
255
0x10 //
十进制数
16
-
0xDAD1 //
十进制数
-56 017
二进制数以
0b
开头，由一个数字（
0
和
1
）序列组成。和其他值一样，二进制数也可以
包含符号 ：
0b01100000 //
十进制数
96
0b00000010 //
十进制数
2
-
0b10 //
十进制数
-2
如果尝试将一个太大的整数存储成整型或将不完全是数字的变量存储成整型，它会自动
被转换为一个浮点数。
可使用
is_int()
函数（或它的别名
is_integer()
）来测试一个值是否是一个整型 ：
if (is_int($x)) {
// $x
是一个整型
}
浮点数
浮点数（通常简称为实数）是由十进制数表示的数值 ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.