subject_24446.htm

一些关于vc的问答

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序号：24446 发表者：硬撅撅 发表日期：2002-12-12 18:59:16
<br>主题：va_start ( ArgumentList, Format );干吗用的？
<br>内容：如题
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<font color=red>答案被接受</font><br>回复者：xiongli 回复日期：2002-12-12 20:02:55
<br>内容：以上是我学c语言的笔记<BR>c里面的函数可以实现未定参数个数传递,里面就需要用到va_start宏<BR>下面是一个例子<BR>具体问题可以看msdn<BR><BR><BR>///////////////////////////////////&nbsp;&nbsp; 第一个程序<BR>#include &lt;stdio.h&gt;<BR>#include &lt;stdarg.h&gt;<BR>double sum_series(int ,...);<BR>main()<BR>{<BR>&nbsp;&nbsp; double d;<BR>&nbsp;&nbsp; d=sum_series(5,0.5,0.25,0.125,0.0625,0.03125);<BR>&nbsp;&nbsp; printf("sum of series is %f\n",d);&nbsp;&nbsp;<BR>}<BR>double&nbsp;&nbsp;sum_series(int num,...)<BR>{<BR>&nbsp;&nbsp;double sum=0.0f;<BR>&nbsp;&nbsp;va_list Vp;<BR>&nbsp;&nbsp;va_start(Vp,num);<BR>&nbsp;&nbsp;for(;num;num--)<BR>&nbsp;&nbsp;{<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; t=va_arg(Vp,double);<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; sum+=t;<BR>&nbsp;&nbsp;}<BR>&nbsp;&nbsp;va_end(Vp);<BR>&nbsp;&nbsp;return(sum);<BR>}<BR>////////////////////////////////////////////////////////////////// <BR>第二个程序<BR><BR>#include &lt;stdio.h&gt;<BR>#include &lt;stdarg.h&gt;<BR>void abc(int,...);<BR>main(<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;abc(4,1234,27.88,'P',"programm c");<BR>}<BR><BR><BR>void abc(int n,...)<BR>{<BR>&nbsp;&nbsp;&nbsp;&nbsp;va_list p;<BR>&nbsp;&nbsp;&nbsp;&nbsp;va_start(p,n);<BR>&nbsp;&nbsp;&nbsp;&nbsp;printf("%d ",va_arg\p,int);&nbsp;&nbsp; ///那个var_arg后面的符号不知道是斜杠还是括号&nbsp;&nbsp;可能是斜杠<BR>&nbsp;&nbsp;&nbsp;&nbsp;printf("%f ",va_arg\p,double);<BR>&nbsp;&nbsp;&nbsp;&nbsp;printf("%c ",va_arg\p,char);<BR>&nbsp;&nbsp;&nbsp;&nbsp;printf("%s ",va_arg\p,char *);<BR>&nbsp;&nbsp;&nbsp;&nbsp;va_end(p);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; //那个var_end也不知道是下划线还是 减号<BR>&nbsp;&nbsp;&nbsp;&nbsp;return;<BR>}<BR>结果&nbsp;&nbsp;1234 27.880000 k programm c <BR><BR>还有&nbsp;&nbsp;void print(char *p,...)<BR>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 还要的话&nbsp;&nbsp; 再说<BR><BR><BR>
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