📄 c++的iostream标准库介绍.htm

📁 C++的iostream标准库介绍。希望能帮助你。
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{ 
        <FONT color=brown>int</FONT> a; 
        cin&gt;&gt;a; 
        cout&lt;&lt;cin.rdstate()&lt;&lt;endl; 
        cin.clear(ios::goodbit); 
        cout&lt;&lt;cin.rdstate()&lt;&lt;endl; 
        system("<FONT color=blue>pause</FONT>"); 
}</PRE><PRE></PRE></DIV>通常当我们发现输入有错又需要改正的时候，使用clear()更改标记为正确后，同时也需要使用get()成员函数清除输入缓冲区，以达到重复输入的目的。 

<P>　　示例代码如下： 
<DIV class=fragment><PRE><FONT color=navy>#include</FONT> &lt;iostream&gt; 
<FONT color=brown>using</FONT> <FONT color=brown>namespace</FONT> std; 

<FONT color=brown>int</FONT> main()  
{ 
        <FONT color=brown>int</FONT> a; 
        <FONT color=brown>while</FONT>(1) 
        { 
                cin&gt;&gt;a; 
                <FONT color=brown>if</FONT>(!cin)<FONT color=green>//条件可改写为cin.fail() </FONT>
                { 
                        cout&lt;&lt;"<FONT color=blue>输入有错!请重新输入</FONT>"&lt;&lt;endl; 
                        cin.clear(); 
                        cin.get(); 
                } 
                <FONT color=brown>else</FONT> 
                { 
                        cout&lt;&lt;a; 
                        <FONT color=brown>break</FONT>; 
                } 
        } 
        system("<FONT color=blue>pause</FONT>"); 
}</PRE><PRE></PRE></DIV>　　最后再给出一个对文件流错误标记处理的例子，巩固学习，代码如下： 
<DIV class=fragment><PRE><FONT color=navy>#include</FONT> &lt;iostream&gt; 
<FONT color=navy>#include</FONT> &lt;fstream&gt; 
<FONT color=brown>using</FONT> <FONT color=brown>namespace</FONT> std; 

<FONT color=brown>int</FONT> main()  
{ 
        ifstream myfile("<FONT color=blue>c:\\1.txt</FONT>",ios_base::in,0); 
        <FONT color=brown>if</FONT>(myfile.fail()) 
        { 
                cout&lt;&lt;"<FONT color=blue>文件读取失败或指定文件不存在!</FONT>"&lt;&lt;endl; 
        } 
        <FONT color=brown>else</FONT> 
        { 
                <FONT color=brown>char</FONT> ch; 
                <FONT color=brown>while</FONT>(myfile.get(ch)) 
                { 
                        cout&lt;&lt;ch; 
                } 
                <FONT color=brown>if</FONT>(myfile.eof()) 
                { 
                        cout&lt;&lt;"<FONT color=blue>文件内容已经全部读完</FONT>"&lt;&lt;endl; 
                } 
                <FONT color=brown>while</FONT>(myfile.get(ch)) 
                { 
                        cout&lt;&lt;ch; 
                } 
        } 
        system("<FONT color=blue>pause</FONT>"); 
}</PRE><PRE></PRE></DIV>
<P>
<P>　　未完待续…… 
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