subject_40661.htm

一些关于vc的问答

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序号：40661 发表者：annehyf1024 发表日期：2003-05-20 15:59:45
<br>主题：怎样将string型的变量（如 string s="12.234")转换成数字12.234
<br>内容：请多指教！
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<font color=red>答案被接受</font><br>回复者：淡淡 回复日期：2003-05-20 16:25:19
<br>内容：double String2Double(CString str){<BR>&nbsp;&nbsp;&nbsp;&nbsp;double db=0;<BR>&nbsp;&nbsp;&nbsp;&nbsp;int temp=1;<BR>&nbsp;&nbsp;&nbsp;&nbsp;char ch;<BR>&nbsp;&nbsp;&nbsp;&nbsp;int comma=str.Find('.');<BR><BR>&nbsp;&nbsp;&nbsp;&nbsp;for (int i=0;i&lt;comma;i++)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{//转换整数部分<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ch=str.GetAt(i);;<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;temp=ch-('1'-1);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;db+=(double)temp*(double)pow(10,comma-i-1);<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR><BR>&nbsp;&nbsp;&nbsp;&nbsp;for(int j=comma+1;j&lt;str.GetLength();j++)<BR>&nbsp;&nbsp;&nbsp;&nbsp;{//转换小数部分<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;ch=str.GetAt(j);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;temp=ch-('1'-1);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;db+=(double)temp*(double)(1/pow(10,j-comma));<BR>&nbsp;&nbsp;&nbsp;&nbsp;}<BR>&nbsp;&nbsp;&nbsp;&nbsp;return db;<BR>}<BR>这是我自己写的函数，你看看吧
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回复者：ohye212 回复日期：2003-05-20 16:32:17
<br>内容：#include &lt;stdlib.h&gt;<BR>#include &lt;stdio.h&gt;<BR><BR>void main( void )<BR>{<BR>&nbsp;&nbsp; char *s; double x; int i; long l;<BR><BR>&nbsp;&nbsp; s = "&nbsp;&nbsp;-2309.12E-15";&nbsp;&nbsp;&nbsp;&nbsp;/* Test of atof */<BR>&nbsp;&nbsp; x = atof( s );<BR>&nbsp;&nbsp; printf( "atof test: ASCII string: %s\tfloat:&nbsp;&nbsp;%e\n", s, x );<BR><BR>&nbsp;&nbsp; s = "7.8912654773d210";&nbsp;&nbsp;/* Test of atof */<BR>&nbsp;&nbsp; x = atof( s );<BR>&nbsp;&nbsp; printf( "atof test: ASCII string: %s\tfloat:&nbsp;&nbsp;%e\n", s, x );<BR><BR>&nbsp;&nbsp; s = "&nbsp;&nbsp;-9885 pigs";&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;/* Test of atoi */<BR>&nbsp;&nbsp; i = atoi( s );<BR>&nbsp;&nbsp; printf( "atoi test: ASCII string: %s\t\tinteger: %d\n", s, i );<BR><BR>&nbsp;&nbsp; s = "98854 dollars";&nbsp;&nbsp;&nbsp;&nbsp; /* Test of atol */<BR>&nbsp;&nbsp; l = atol( s );<BR>&nbsp;&nbsp; printf( "atol test: ASCII string: %s\t\tlong: %ld\n", s, l );<BR>}<BR><BR><BR>Output<BR><BR>atof test: ASCII string:&nbsp;&nbsp; -2309.12E-15&nbsp;&nbsp; float:&nbsp;&nbsp;-2.309120e-012<BR>atof test: ASCII string: 7.8912654773d210&nbsp;&nbsp; float:&nbsp;&nbsp;7.891265e+210<BR>atoi test: ASCII string:&nbsp;&nbsp; -9885 pigs&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;integer: -9885<BR>atol test: ASCII string: 98854 dollars&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;long: 98854<BR><BR>
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回复者：Fang 回复日期：2003-05-20 17:36:41
<br>内容：atof不是挺好的嘛。
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回复者：annehyf1024 回复日期：2003-05-21 10:04:34
<br>内容：是啊！可是我定义的数据类型是string,atof只能对char *类型的数据进行直接转换。<BR>如果用atof进行转换的话，还要把string型数据转换为char *型，我是用这种最笨的方法转换的。<BR>string s;<BR>char * t;<BR>for (int i=0;i&lt;s.length();i++)<BR>t[i]=s[i];<BR>还有一种方法，是用strcpy(t,s),但是s必须这样定义CString s;我是编的Win32 console Application程序，为什么声明CString s不行呢？（我加的头文件有：#include&lt;string&gt;<BR>#include&lt;stdlib.h&gt;)<BR>
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回复者：Fang 回复日期：2003-05-21 12:36:11
<br>内容：string 转换到 char*, 并不困难，代价也很低。<BR>char *p = s.c_str();即可。<BR><BR>double f = atof(s.c_str());<BR><BR>应该就可以了。<BR><BR>当然了，第一楼写的String2Double当然没问题，学习学习总是好的，加深理解嘛。<BR><BR>可是，如果想吃饭要自己烧，想建房还要自己造砖头，这也太兴师动众了。
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回复者：applepolisher 回复日期：2003-06-01 17:30:16
<br>内容：c_str()是什么呀，哈哈
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回复者：异乡客 回复日期：2003-06-12 11:48:30
<br>内容：我怎么试不出来1楼的程序
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回复者：lijb 回复日期：2003-06-12 17:25:52
<br>内容：&nbsp;&nbsp;&nbsp;&nbsp;CString m_str="12.3456";<BR>&nbsp;&nbsp;&nbsp;&nbsp;double f =atof(m_str);<BR><BR><BR>这就行了，那有那么麻烦。
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