【C++ Primer】【学习笔记】【第三章】标准库类型之：string类型

古城微笑少年丶 2022-08-06 03:16 153阅读 0赞

本章讲解如下三种标准库类型： **string**、 **vector**、 **bitset**。其中，string定义了大小可变的字符串；vector用于保存一组指定类型的对象；bitset提供了一种抽象方法来操作位的集合。

**命名空间的using声明**

注：为避免名字冲突，要避免使用using指示，而应当使用using声明。两者表示如下：

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     <strong style="background-color:inherit">方式</strong> 
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   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:279px"> <strong style="background-color:inherit">示例</strong></td> 
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      using指示： 
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    <div style="min-width:2px; background-color:inherit">
      using namespace std; 
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      using声明： 
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      using std::cin; 
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      using std::cout; 
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    <div style="min-width:2px; background-color:inherit">
      using std::endl; 
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**标准库string类型**

1、几种初始化string类对象的方式如下：

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     <strong style="background-color:inherit">方式</strong> 
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     <strong style="background-color:inherit">含义</strong> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">string s1;</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">默认构造函数</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">string s2(s1);</span> 
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    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:Microsoft Yahei; background-color:inherit">将s2初始化为s1的一个副本</span> 
    </div> </td> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">string s3("value");</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">将s3初始化为一个字符串字面值副本</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">string s4(n, 'c');</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">将s4初始化为字符'c'的n个副本</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">string s5((char *str), n);</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">将s5初始化为从str开始的n个字符</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit"><span style="color:#000000; background-color:rgb(255,255,255); font-style:normal; font-weight:normal; line-height:normal">string s6("value", n);</span><br style="background-color:inherit"> </span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">将s6初始化为从"value"第一个字符开始往后的n个字符组成的字符串副本</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">string s7(s1, n);</span> 
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     <span style="font-family:Microsoft Yahei; background-color:inherit">将s7初始化为从s1的第一个字符开始<strong style="background-color:inherit">跳过n个</strong>字符后剩余的字符串副本</span> 
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2、string对象的读写

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       string s; 
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       cin &gt;&gt; s; 
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     <br style="background-color:inherit"> 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit"> 
     <div style="background-color:rgb(255,255,255); color:rgb(0,0,0); font-family:微软雅黑; font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">
       这两句代码是指从标准输入读取字符串并存储到s当中，读取的原则如下： 
     </div> 
     <div style="background-color:rgb(255,255,255); color:rgb(0,0,0); font-family:微软雅黑; font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">
       a. 忽略开头的所有空白字符（如：空格、换行符、制表符等）； 
     </div> 
     <div style="background-color:rgb(255,255,255); color:rgb(0,0,0); font-family:微软雅黑; font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">
       b. 读取字符直到再次遇到空白字符为止（该空白字符仍然留在输入流中）。 
     </div> 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">string line;</span> 
    </div> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">getline(cin, line);</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit"> 
     <div style="background-color:rgb(255,255,255); color:rgb(0,0,0); font-family:微软雅黑; font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">
       这两句代码是指从标准输入读取字符串并存储到s当中，读取的原则如下： 
     </div> 
     <div style="background-color:rgb(255,255,255); color:rgb(0,0,0); font-family:微软雅黑; font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">
       a. 不忽略开头的空白字符（如：空格、制表符等，不包含换行符）； 
     </div> 
     <div style="background-color:rgb(255,255,255); color:rgb(0,0,0); font-family:微软雅黑; font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:1.5">
       b. 读取字符直到遇到换行符符为止（换行符从输入流中去掉，但并不存储在string对象中）。 
     </div> 
    </div> </td> 
  </tr> 
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</table>

**样例一（cin读入字符串）**：

#include <iostream>
    #include <string>
    using std::cin;
    using std::cout;
    using std::endl;
    using std::string;
    int main()
    {
            string s;
            cin >> s;
            cout << s << endl;
            return 0;
    }

输出：

[chapter3]$ ./a.out 
          Hello World!
    Hello

**样例二（cin循环读取，并将单词逐个输出）**：

**说明：cin >> word语句一般返回true，只有当读取到EOF时返回false。**

#include <iostream>
    #include <string>
    using std::cin;
    using std::cout;
    using std::endl;
    using std::string;
    int main()
    {
            string word;
            while (cin >> word)
            {
                    cout << word << endl;
            }
            cout << "end ok\n";
            return 0;
    }

输出：

[chapter3]$ ./a.out 
    a 
    a 
    b 
    b 
    c 
    c 
    <Ctrl + D>
    end ok

**样例三（使用getline函数读取整行文本）**：

**说明：getline(cin, line)语句同cin >> word一样，一般返回true，只有当读取到EOF时返回false。**

#include <iostream>
    #include <string>
    using std::cin;
    using std::cout;
    using std::endl;
    using std::string;
    int main()
    {
            string line;
            while (getline(cin, line))
            {
                    cout << line << endl;
            }
            cout << "end ok" << endl;
            return 0;
    }

输出：

[chapter3]$ ./a.out 
    a b c 
    a b c 
    d e f 
    d e f 
    end ok

3、string对象的操作

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     <strong style="background-color:inherit">操作</strong> 
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     <strong style="background-color:inherit">含义</strong> 
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      s.empty() 
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      判断s是否为空，是则返回true，否则返回false 
    </div> </td> 
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      s.size() 
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    <div style="min-width:2px; background-color:inherit">
      返回s中字符的个数；该函数的返回类型为 
     <strong style="background-color:inherit">string::size_type</strong>，为一个无符号数，至于是unsigned int还是unsigned long由机器决定。 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit">
      s[n] 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit">
      返回s中位置为n的字符，位置从0开始计数。这里的下标n的类型最好也使用 
     <strong style="background-color:inherit">string::size_type</strong>。 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit">
      s1 + s2 
    </div> 
    <div style="min-width:2px; background-color:inherit">
      s1 + "string" 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:408.5999755859375px"> 
    <div style="min-width:2px; background-color:inherit">
      将s1和s2连接成一个新的字符串，并返回新生成的字符串。 
    </div> 
    <div style="min-width:2px; background-color:inherit">
      字符串进行连接时，+操作符的左右操作数必须至少有一个是string类型的（即：两个字符串字面值相加是非法的），并且+操作返回一个新的string对象。 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit">
      s1 = s2 
    </div> </td> 
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    <div style="min-width:2px; background-color:inherit">
      把s1的内容替换成s2的副本 
    </div> </td> 
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      s1 == s2 
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      比较s1和s2的内容，相等则返回true，不等则返回false。这里相等的含义是：长度相同，并且含有相同的字符。 
    </div> </td> 
  </tr> 
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    <div style="min-width:2px; background-color:inherit">
      !=, &gt;, &gt;=, &lt;, &lt;= 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:408.5999755859375px"> 
    <div style="min-width:2px; background-color:inherit">
      保持惯有含义，参考 == 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

**样例一（string的empty和size操作）**：

注：判断字符串为空的两种方法：a. 使用s.empty()进行判断；b. 使用s.size()是否为0进行判断。

#include <iostream>
    #include <string>
    using namespace std;
    int main()
    {
            string str("Baidu is a good company\n");
            cout << "The size of: " << str << "is " << str.size()
                     << " characters, including the newline." << endl;
            string str2;
            if (str2.size() == 0)
            {
                    cout << "Method of size: str2 is empty." << endl;
            }
            if (str2.empty())
            {
                    cout << "Method of empty: str2 is empty." << endl;
            }
            return 0;
    }

输出：

[chapter3]$ ./a.out 
    The size of: Baidu is a good company 
    is 24 characters, including the newline. 
    Method of size: str2 is empty. 
    Method of empty: str2 is empty.

**样例二（读取string中的字符）**：

#include <iostream>
    #include <string>
    using namespace std;
    int main()
    {
            string str("Baidu is a good company\n");
            for (string::size_type i = 0; i < str.size(); i++)
            {
                    cout << str[i] << endl;
            }
            return 0;
    }

输出：

[chapter3]$ ./a.out 
    B 
    a 
    i 
    d 
    u 
    
    i 
    s 
    
    a 
    
    g 
    o 
    o 
    d 
    
    c 
    o 
    m 
    p 
    a 
    n 
    y

4、string对象中字符的处理

<table style="font-size:undefined; border-collapse:collapse; margin-top:10px; margin-bottom:10px; display:table; background-color:inherit; width:626px"> 
 <tbody style="background-color:inherit"> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <strong style="background-color:inherit">cctype头文件定义的函数</strong> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <strong style="background-color:inherit">说明</strong> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit">
      isalnum(c) 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit">
      如果c是字母或数字，则为true。 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isalpha(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是字母，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">iscntrl(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal"><span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是控制字符，则为true。</span></span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isdigit(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal"><span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是数字，则为true。</span></span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isgraph(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal"><span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c不是空格，但可以打印，则为true。</span></span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">islower(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是小写字母，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isprint(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25.99998779296874px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是可打印字符，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">ispunct(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是标点符号，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isspace(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是空白字符，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isupper(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是大写字母，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">isxdigit(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是十六进制数，则为true。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">tolower(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是大写字母，则返回其小写字母形式，否则直接返回c。</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
  <tr style="background-color:inherit"> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:178.1999994277954px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">toupper(c)</span> 
     <br style="background-color:inherit"> 
    </div> </td> 
   <td style="word-break:break-all; border:1px solid rgb(153,153,153); padding:5px 10px; min-height:25px; min-width:25px; height:25px; background-color:inherit; width:406.20000000000005px"> 
    <div style="min-width:2px; background-color:inherit"> 
     <span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal"><span style="font-family:微软雅黑; color:#000000; background-color:rgb(255,255,255); font-size:14.399999618530273px; font-style:normal; font-weight:normal; line-height:normal">如果c是小写字母，则返回其大写字母形式，否则直接返回c。</span></span> 
     <br style="background-color:inherit"> 
    </div> </td> 
  </tr> 
 </tbody> 
</table>