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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="title2"><b>4.2.2 递归预测分析器的构造</b></font>   
 
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<p>      
文法(4.1)的预测分析器，由图4.3中所示的一组递归过程组成，这组递归过程的执行，实现根据文法（4.1）对任一输入w进行预测分析。因此，这个分析器称为递归预测分析器。</p>     
<p> <br>
<font color=blue>PROCEDURE</font> match(t:token);<br>    
&nbsp; <font color=blue>BEGIN</font><br>     
&nbsp;&nbsp;&nbsp;&nbsp; <font color=blue>IF</font> lookahead=t<br>     
&nbsp;&nbsp;&nbsp;&nbsp; <font color=blue>THEN</font> lookahead:=nexttoken<br>     
&nbsp;&nbsp;&nbsp;&nbsp; <font color=blue>ELSE</font> error<br>     
&nbsp; <font color=blue>END</font>;<br><br>     
<font color=blue>PROCEDURE</font> type;<br>     
&nbsp; <font color=blue>BEGIN</font><br>     
&nbsp;&nbsp;&nbsp; <font color=blue>IF</font> lookahead in {integer, char, num} <font color=blue>THEN</font> &nbsp;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; simple&nbsp;&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">ELSE IF</font> lookahead=‘<img src="images/shy.gif">’
<font color="#0000FF"> 
THEN BEGIN</font><br>     
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match(‘<img src="images/shy.gif">’);  
match(id);&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">END</font>&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">ELSE IF</font> lookahead=array <font color="#0000FF"> THEN BEGIN</font><br>     
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match(array); match(‘[’); simple;<br>  &nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match(‘]’); 
match(of); type&nbsp;&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">END</font><br>    
&nbsp;&nbsp;&nbsp; <font color="#0000FF">ELSE</font> error<br>     
&nbsp; <font color="#0000FF">END</font>;<br><br>
<font color="#0000FF">
PROCEDURE</font> simple;<br>     
&nbsp; <font color="#0000FF">BEGIN</font><br>    
&nbsp;&nbsp;&nbsp; <font color="#0000FF">IF</font> lookahead=integer <font color="#0000FF">THEN</font>&nbsp;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match(integer)&nbsp;&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">ELSE</font> <font color="#0000FF">IF</font> lookahead=char 
<font color="#0000FF">THEN</font>&nbsp;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match(char)&nbsp;&nbsp;&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">ELSE IF</font> lookahead=num&nbsp; <font color="#0000FF"> THEN BEGIN</font>&nbsp;<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; match(num);&nbsp; match(dotdot); match(num)&nbsp;&nbsp;&nbsp;<br>
&nbsp;&nbsp;&nbsp; <font color="#0000FF">END</font><br>    
&nbsp;&nbsp;&nbsp; <font color="#0000FF">ELSE</font>&nbsp; error<br>     
&nbsp; <font color="#0000FF">END</font>;</p>
<p align="center">图4.3 一个预测分析器的伪代码</p>     
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