编译原理实验1扫描器的设计与实现

1实验1:扫描器的设计与实现1.1.目的和要求1．加深对词法分析理论的理解，培养动手实践的能力。2．学会从以字符串表示的源程序中识别出具有独立意义的基本语法单位，同时指出它们的属性的方法和技术。1.2.实验环境WindowsXP+WinTC1911.3.实验准备1、先将课本3.5节词法分析程序的生成认真的学习一遍，理解词法分析程序的构成过程。2、写出C语言测试程序，分析可能得到的结果。测试程序：#definepi3.14voidmain(){doubler=2.5;doubles=0.0;s=pi*r*r;printf(%f,s);}预测结果：(513,#)(14,define)(100,pi)(200,3)(514,.)(200,14)(1,void)(2,main)(502,()(503,))(506,{)(15,double)(100,r)(402,=)(200,2)(514,.)(200,5)(501,;)(15,double)(100,s)(402,=)(200,0)(514,.)(200,0)(501,;)(100,s)(402,=)(100,pi)(416,*)(100,r)(416,*)(100,r)(501,;)(12,printf)(502,()(509,)(511,%)(100,f)(509,)(512,,)(100,s)(503,))(501,;)(507,})1.4.实验内容及步骤1、输入已给的文本格式的扫描程序Lexical.c文件，然后编译运行，检查修改错误。22、编译成功后，提示输入C语言测试程序，用回车键查看输出的单词流，即单词符号及其属性。3、比较自己分析的结果和屏幕上的输出结果。1.5.实验小结1、得到的经验。通过本次实验，我了解了如何设计、编制并调试词法分析程序，加深了对词法分析原理的理解。同时，在编制和调试程序时要全面考虑，避免漏掉或者错误定义定界符等，造成不必要的错误。2、遇到的主要问题。忘记对空格、回车符等定界符进行设置等。3、改进方案。3（1）char*keywords[15]={void,main,if,then,break,int,char,float,include,for,while,printf,scanf,define,double};（2）case13:{flag=14;status=1;break;}case14:{flag=15;status=1;break;}（3）case'.':{words[j]=ch;words[j+1]='\0';flag=514;break;}case'':{words[j]='';flag=250;break;}case'\n':{flag=251;break;}（4）elseif(flag==250||flag==251){}修改前源代码：#includestdio.h#includestdlib.h#includestring.hinti,j,k,flag,number,status;4/*statuswhichisusetojudgethestringiskeywordsornot!*/charch;charwords[10]={};charprogram[500];intScan(charprogram[]){char*keywords[13]={void,main,if,then,break,int,char,float,include,for,while,printf,scanf};number=0;status=0;j=0;ch=program[i++];/*Tohandlethelettlespaceandstab*//*handleletters*/if((ch='a')&&(ch='z')){while((ch='a')&&(ch='z')){words[j++]=ch;ch=program[i++];}i--;words[j++]='\0';for(k=0;k13;k++)if(strcmp(words,keywords[k])==0)switch(k){case0:{flag=1;status=1;break;}case1:{flag=2;status=1;5break;}case2:{flag=3;status=1;break;}case3:{flag=4;status=1;break;}case4:{flag=5;status=1;break;}case5:{flag=6;status=1;break;}case6:{flag=7;status=1;break;}case7:{flag=8;status=1;break;}case8:{flag=9;status=1;break;6}case9:{flag=10;status=1;break;}case10:{flag=11;status=1;break;}case11:{flag=12;status=1;break;}case12:{flag=13;status=1;break;}}if(status==0){flag=100;}}/*handledigits*/elseif((ch='0')&&(ch='9')){number=0;while((ch='0')&&(ch='9')){number=number*10+(ch-'0');ch=program[i++];}7flag=200;i--;}/*opereationandedgehandle*/elseswitch(ch){case'=':{if(ch=='=')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=401;}else{i--;flag=402;}break;}case'':{if(ch=='')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=403;}else8{i--;flag=404;}break;}case'':{if(ch=='')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=405;}else{i--;flag=406;}break;}case'!':{if(ch=='!')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=407;}else9{i--;flag=408;}break;}case'+':{if(ch=='+')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=409;}elseif(ch=='+'){words[j++]=ch;words[j]='\0';flag=410;}else{i--;flag=411;}break;}case'-':{if(ch=='-')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='=')10{words[j++]=ch;words[j]='\0';flag=412;}elseif(ch=='-'){words[j++]=ch;words[j]='\0';flag=413;}else{i--;flag=414;}break;}case'*':{if(ch=='*')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=415;}else{i--;flag=416;}break;}11case'/':{if(ch=='/')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=417;}else{i--;flag=418;}break;}case';':{words[j]=ch;words[j+1]='\0';flag=501;break;}case'(':{words[j]=ch;words[j+1]='\0';flag=502;break;}case')':{words[j]=ch;words[j+1]='\0';flag=503;break;}12case'[':{words[j]=ch;words[j+1]='\0';flag=504;break;}case']':{words[j]=ch;words[j+1]='\0';flag=505;break;}case'{':{words[j]=ch;words[j+1]='\0';flag=506;break;}case'}':{words[j]=ch;words[j+1]='\0';flag=507;break;}case':':{words[j]=ch;words[j+1]='\0';flag=508;break;}case'':{words[j]=ch;words[j+1]='\0';flag=509;break;}13case'%':{if(ch=='%')words[j++]=ch;words[j]='\0';ch=program[i++];if(ch=='='){words[j++]=ch;words[j]='\0';flag=510;}else{i--;flag=511;}break;}case',':{words[j]=ch;words[j+1]='\0';flag=512;break;}case'#':{words[j]=ch;words[j+1]='\0';flag=513;break;}case'@':{words[j]='#';flag=0;break;}default:{14flag=-1;break;}}returnflag;}main(){i=0;printf(pleaseinputaprogramendwith@);do{ch=getchar();program[i++]=ch;}while(ch!='@');i=0;do{flag=Scan(program);if(flag==200){printf((%2d,%4d),flag,number);}elseif(flag==-1){printf((%d,error),flag);}else{printf((%2d,%4s),flag,words);}}while(flag!=0);system(pause);}修改后源代码：#includestdio.h15#includestdlib.h#includestring.hinti,j,k,flag,number,status;/*statuswhichisusetojudgethestringiskeywordsornot!*/charch;charwords[10]={};charprogram[500];intScan(charprogram[]){char*keywords[15]={void,main,if,then,break,int,char,float,include,for,while,printf,scanf,define,double};number=0;status=0;j=0;ch=program[i++];/*Tohandlethelettles