4.2.2.2b.htm
来自「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」· HTM 代码 · 共 72 行
HTM
72 行
<html>
<head>
<title>编译原理</title>
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</p>
<p><font color="#0000FF">
PROCEDURE</font> E;<br>
<font color="#0000FF">BEGIN</font><br>
T;<br>
<font color="#0000FF">WHILE</font> lookahead='+'
<font color="#0000FF"> DO</font><br>
<font color="#0000FF">BEGIN</font><br>
match('+');T<br>
<font color="#0000FF">END</font><br>
<font color="#0000FF">END</font>;<br>
<br>
<font color="#0000FF">PROCEDURE</font> T;<br>
<font color="#0000FF">BEGIN</font><br>
F;<br>
<font color="#0000FF">WHILE</font> lookahead='*'
<font color="#0000FF"> DO</font><br>
<font color="#0000FF">BEGIN</font><br>
match('*');F<br>
<font color="#0000FF">END</font><br>
<font color="#0000FF">END</font>;<br>
<br>
<font color="#0000FF">PROCEDURE</font> F;<br>
<font color="#0000FF">BEGIN</font><br>
<font color="#0000FF">IF</font>
lookahead='(' <font color="#0000FF">THEN</font> <br>
<font color="#0000FF">BEGIN</font><br>
match('(');E;match(')')<br>
<font color="#0000FF">END</font><br>
<font color="#0000FF">ELSE IF</font>
lookahead=id <font color="#0000FF">THEN</font> <br>
match(id);<br>
<font color="#0000FF">ELSE</font> error<br>
<font color="#0000FF">END</font>;
</p>
<p>
match过程参见图4.2。 </p>
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<p>如果用某种语言来描述预测分析器,只有当该语言允许递归调用时才能实现。实现预测分析器的另一种不含递归调用的有效方法是使用一张分析表和一个栈进行联合控制。这就是下一节所要介绍的。
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