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📁 建立《编译原理网络课程》的目的不仅使学生掌握构造编译程序的原理和技术
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<font class="content"><font color="#0000FF">%{</font><br>
<font color="#0000FF">
      #include</font> &lt;ctype.h&gt;<br>   
<font color="#0000FF">  
      #include</font> &lt;stdio.h&gt;<br>   
<font color="#0000FF">  
      #define</font> YYSTYPE double /*Yacc栈定义为double类型*/<br>   
<font color="#0000FF">  
      %}</font><br>
<font color="#0000FF">%</font>token NUMBER<br>   
<font color="#0000FF">%</font>left '+' '-'<br>   
<font color="#0000FF">%</font>left '*' '/'<br>   
<font color="#0000FF">%</font>right UMINUS<br>   
<font color="#0000FF">  
      %%</font><br>
      lines&nbsp; :lines expr '\n'&nbsp; {printf(&quot;%g\n&quot;,$2);}<br>   
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |lines '\n'<br>   
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |/*<span style="mso-bidi-font-size: 12.0pt; font-family: 宋体; mso-bidi-font-family: Times New Roman; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA">empty*/<br>  
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|error'\n' {yyerror(&quot;&quot;reenter last  
      line:&quot;);<br>
      </span></font>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;   
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;yyerrok;}<font class="content"><span style="mso-bidi-font-size: 12.0pt; font-family: 宋体; mso-bidi-font-family: Times New Roman; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA"><br>
      &nbsp;&nbsp;&nbsp;&nbsp; ;<br> 
      expr&nbsp;&nbsp;&nbsp;:expr '+' expr {$$=$1+$3;}<br>  
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |expr '-' expr   
      {$$=$1-$3;}<br>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |expr '*' expr   
      {$$=$1*$3;}<br>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;|expr '/' expr   
      {$$=$1/$3;}<br>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |'(' expr %   
      ')'{$$=$2;}<br>
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; | '-' expr %prec   
      UMINUS {$$=-$2;}<br>  
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;| NUMBER<br>  
      &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;;<br>  
<font color="#0000FF"> 
      %%</font><br>
<font color="#0000FF">
      #include</font> &quot;lex.yy.c&quot;</span></font> 
      </p>
     &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;图4.32 &nbsp;&nbsp;有错误恢复的台式计算器 
      
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