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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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<b>例5.19</b>  表5.10中使用了三个标记非终结符号L,M和N，以使得当B的子树被归约时，继承属性B.ps的值在分析栈中的位置是可知的。原来的语法制导定义在表5.7中给出，与其相应的说明在例5.13中已经解释了。     
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<center>表5.10 &nbsp所有继承属性都由复写规则赋值</center>    
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<td width="42%" height=30 align=center>产生式</td>
<td width="58%" align=center>语义规则</td>
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	<br>
	<p>S -> L B<br></p>    
	<br>
	<p>L -> ε</p>    
	<p>B -> B<sub>1</sub> M B<sub>2</sub><br></p>    
	<br><br><br>
	<p>B -> B<sub>1</sub> sub N B<sub>2</sub></p>
	<br><br><br><br>
	<p>B -> <b>text</b></p>
	<p>M -> ε</p>   
	<p>N -> ε</p>   
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        <p>&nbsp&nbsp;B.ps := L.s<br>   
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;S.ht := B.ht</p>   
	<p>&nbsp&nbsp;L.s := 10</p>  
	<p>&nbsp&nbsp;B<sub>1</sub>.ps := B.ps<br>  
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;M.i := B.ps<br>  
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;B<sub>2</sub>.ps := M.s<br>  
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;B.ht := max(B<sub>1</sub>.ht,B<sub>2</sub>.ht)</p>  
	<p>&nbsp&nbsp;B<sub>1</sub>.ps := B.ps<br>  
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;N.i := B.ps<br>  
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;B<sub>2</sub>.ps := N.s<br> 
	&nbsp&nbsp&nbsp&nbsp&nbsp&nbsp;B.ht := disp(B<sub>1</sub>.ht,B<sub>2</sub>.ht)</p>  
	<p>&nbsp&nbsp;B.ht := <b>text</b>.h&#215B.ps</p> 
	<p>&nbsp&nbsp;M.s := M.i</p> 
	<p>&nbsp&nbsp;N.s := shrink(N.i)</p> 
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