编译原理实验报告解析

1、编译原理实验报告语义分析实验：班级：姓名：学号：一、实验目的：通过上机实习，加深对语法制导翻译原理的理解，掌握将语法分析所识别的语法成分变换为中间代码的语义翻译方法。二、实验要求：采用递归下降语法制导翻译法，对算术表达式、赋值语句进行语义分析并生成四元式序列。三、算法思想：1、设置语义过程。(1)emit(char*result,char*ag1,char*op,char*ag2)该函数的功能是生成一个三地址语句送到四元式表中。四元式表的结构如下：structcharresult8;charag18;charop8;charag28;quad20;(2)char*newtemp()该函数回送一

2、个新的临时变量名，临时变量名产生的顺序为Tl,T2,char*newtemp(void)char*p;charm8;p=(char*)malloc(8);k+;itoa(k,m,10);strcpy(p+1,m);p0='t'return(p);2、函数lrparser在原来语法分析的基础上插入相应的语义动作：将输入串翻译成四元式序列。在实验中我们只对表达式、赋值语句进行翻译。四、源程序代码：#include<stdio.h>#include<string.h>#include<iostream.h>#include<stdlib.h&

3、gt;structcharresult12;charag112;charop12;charag212;quad;charprog80,token12;charch;intsyn,p,m=O,n,sum=O,kk;p是缓冲区prog的指针，m是token的指针char*rwtab6="begin","if","then","while","do","end"voidscaner();char*factor(void);char*term(void);char*expressio

4、n(void);intyucu();voidemit(char*result,char*ag1,char*op,char*ag2);char*newtemp();intstatement();intk=0;voidemit(char*result,char*ag1,char*op,char*ag2)strcpy(quad.result,result);strcpy(quad.ag1,ag1);strcpy(quad.op,op);strcpy(quad.ag2,ag2);cout<<quad.result<<"="<<quad.ag1&l

5、t;<quad.op<<quad.ag2<<endl;char*newtemp()char*p;charm12;p=(char*)malloc(12);k+;itoa(k,m,10);strcpy(p+1,m);p0='t'return(p);voidscaner()for(n=0;n<8;n+)tokenn=NULL;ch=progp+;while(ch='')ch=progp;p+;if(ch>='a'&&ch<='z')|(ch>='A'&

6、amp;&ch<='Z')m=0;while(ch>='0'&&ch<='9')|(ch>='a'&&ch<='z')|(ch>='A'&&ch<='Z')tokenm+=ch;ch=progp+;tokenm+='0'p-;syn=10;for(n=0;n<6;n+)if(strcmp(token,rwtabn)=0)syn=n+1;break;elseif(ch

7、>='0'&&ch<='9')sum=0;while(ch>='0'&&ch<='9')sum=sum*10+ch-'0'ch=progp+;p-;syn=11;if(sum>32767)syn=-1;elseswitch(ch)case'<':m=0;tokenm+=ch;ch=progp+;if(ch='>')syn=21;tokenm+=ch;elseif(ch='=')syn=22;to

8、kenm+=ch;elsesyn=23;p-;break;case'>':m=0;tokenm+=ch;ch=progp+;if(ch='=')syn=24;tokenm+=ch;elsesyn=20;p-;break;case':':m=0;tokenm+=ch;ch=progp+;if(ch='=')syn=18;tokenm+=ch;elsesyn=17;p-;break;case'*':syn=13;token0=ch;break;case'/':syn=14;token0=ch;br

9、eak;case'+':syn=15;token0=ch;break;case'-':syn=16;token0=ch;break;case'=':syn=25;token0=ch;break;case'':syn=26;token0=ch;break;case'(':syn=27;token0=ch;break;case')':syn=28;token0=ch;break;case'#':syn=0;token0=ch;break;default:syn=-1;break;intl

10、rparser()/coutvv"调用lrparser"vvendl;intschain=0;kk=0;if(syn=1)scaner();schain=yucu();if(syn=6)scaner();if(syn=0&&(kk=0)cout<<"success!"<<endl;elseif(kk!=1)coutvv"缺end!"vvendl;kk=1;elsecoutvv"缺begin!"vvendl;kk=l;return(schain);intyucu()/coutv

11、v"调用yucu"vvendl;intschain=0;schain=statement();while(syn=26)scaner();schain=statement();return(schain);intstatement()/coutv<"调用statement"vvendl;char*eplace,*tt;eplace=(char*)malloc(12);tt=(char*)malloc(12);intschain=0;switch(syn)case10:strcpy(tt,token);scaner();if(syn=18)scane

12、r();strcpy(eplace,expression();emit(tt,eplace,"","");schain=0;elsecoutvv"缺少赋值符!"vvendl;kk=1;return(schain);break;return(schain);char*expression(void)char*tp,*ep2,*eplace,*tt;tp=(char*)malloc(12);ep2=(char*)malloc(12);eplace=(char*)malloc(12);tt=(char*)malloc(12);strcpy(

13、eplace,term();/调用term分析产生表达式计算的第一项eplacewhile(syn=15)|(syn=16)if(syn=15)strcpy(tt,"+"elsestrcpy(tt,"-");scaner();strcpy(ep2,term();调用term分析产生表达式计算的第一项ep2strcpy(tp,newtemp();emit(tp,eplace,tt,ep2);调用newtemp产生临时变量tp存储计算结果/生成四元式送入四元式表strcpy(eplace,tp);return(eplace);char*term(void)/

14、coutvv"调用term"vvendl;char*tp,*ep2,*eplace,*tt;tp=(char*)malloc(12);ep2=(char*)malloc(12);eplace=(char*)malloc(12);tt=(char*)malloc(12);strcpy(eplace,factor();while(syn=13)|(syn=14)if(syn=13)strcpy(tt,"*"elsestrcpy(tt,"/");scaner();strcpy(ep2,factor();strcpy(tp,newtemp()

15、;调用factor分析产生表达式计算的第一项ep2调用newtemp产生临时变量tp存储计算结果emit(tp,eplace,tt,ep2);/生成四元式送入四元式表strcpy(eplace,tp);return(eplace);char*factor(void)char*fplace;fplace=(char*)malloc(12);strcpy(fplace,"");if(syn=10)strcpy(fplace,token);/将标识符token的值赋给fplacescaner();elseif(syn=11)itoa(sum,fplace,10);scaner()

16、;elseif(syn=27)scaner();fplace=expression();/调用expression分析返回表达式的值if(syn=28)scaner();elsecoutvv"缺)错误!"vvendl;kk=1;elsecoutvv"缺(错误!"vvendl;kk=1;return(fplace);voidmain()p=0;cout<<*语义分析程序*"vvendl;cout<<"Pleaseinputstring:"<<endl;docin.get(ch);progp+=ch;while(ch!='#');p=0;scaner();lrparser();五、结果验证：1、给定源程序begina:=2+3*4;x:=(a+b)/cend#输出