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Windows XP + WinTC1911.3. 实验准备1、先将课本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： #define pivoid main()double r = ;double s = ;s = pi*r*r;printf(%f,s);预测结果：(513,#)(14,define)

2、(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,;)

3、(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文件，然后编译运行，检查修改错 误。2、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。伙脣译原1谊El DC-1AL驭i询please input a program end with ttdFine pi 3.It uoid main()double r = 2.5;doubles = 0.0;s = pi*r*r;printf,s) ji aj匚1513,tt)(14 define )(100,pi)(200,.1(200,It)( l,uo502,()(503,Desos,)(15,

4、double)(100,r)(402=)(209,(200s5)(501,;)(15sdouble)(100,s)(402,=)(200,9)(514,)(501,;)(100,s)(402,=)(100,pi)(416,*)(100,r)(416,)(501,;)(12,printf)(502,0 ( 509,*)(511rX)(100ff)(509fJ(100,5)(503,)1501,=)(507,IX讥ttJPress曰iw kc io3、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

5、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。（1）char *keywords15 = void,main,if,then,break,int,char,float,inc lude,for,while,printf,scanf,define,double;（2）case 13:flag = 14;status = 1;break;case 14: flag = 15; status = 1; break;（3）case.: wordsj = ch; wordsj+1 =

6、 0; flag = 514; break;case : wordsj = ;flag = 250;break;casen:flag = 251;break;(4) else if(flag = 250|flag = 251)修改前源代码：#include #include#include int i,j,k,flag,number,status;/*status which is use to judge the string is keywords or not!*/ char ch;char words10 = ;char program500;int Scan(char program

7、)char *keywords13 =void,main,if,then,break,int,char,float,inc lude,for,while,printf,scanf;number = 0;status = 0;j = 0;ch = programi+;/* To handle the lettle space andstab*/*handle letters*/if (ch = a) & (ch = a) & (ch = z )wordsj+=ch;ch=programi+;i-;wordsj+ = 0;for (k = 0; k = 0) & (ch = 0 ) & (ch :

8、if (ch = ) wordsj+ = ch; wordsj = 0; ch= programi+; if (ch = =)wordsj+ = ch;flag = 403;elsei-;flag = 404;break;case:if (ch = = a) & (ch = a) & (ch = z )wordsj+=ch;ch=programi+;i-;wordsj+ = 0;for (k = 0; k = 0) & (ch = 0 ) & (ch :if (ch = ) wordsj+ = ch;wordsj = 0;ch= programi+; if (ch = =) wordsj+ =

9、 ch;wordsj = 0;flag = 403;elsei-;break;case:if (ch = )wordsj+ = ch;wordsj = 0; ch= programi+;if (ch = =)wordsj+ = ch;wordsj= 0;flag = 405;elsei-;flag = 406;break;case!:if (ch = !) wordsj+ = ch; wordsj= 0;ch = programi+;if (ch = =)wordsj+ = ch;wordsj= 0; flag= 407;elsei-;flag = 408;break;case+:if (ch

10、 = +) wordsj+ = ch; wordsj = 0; ch= programi+; if (ch = =)wordsj+ = ch;wordsj = 0; flag= 409;else if (ch = +)wordsj = 0;flag= 410;elsei-;flag= 411;break;case-:if (ch = -)wordsj+ = ch;wordsj = 0;ch= programi+; if (ch = =)wordsj+ = ch;wordsj = 0;flag = 412;else if( ch = -)wordsj+ = ch;wordsj = 0;flag

11、= 413;elsei-;flag = 414;break;case*:if (ch = *) wordsj+ = ch;wordsj = 0;ch= programi+;if (ch = =)wordsj+ = ch; wordsj = 0; flag = 415;elsei-;flag = 416;break;case/: if (ch = /) wordsj+ = ch; wordsj = 0; ch= programi+;if (ch = =)wordsj+ = ch;wordsj = 0; flag= 417;elsei-;flag = 418;break;case;:wordsj

12、= ch; wordsj+1 = 0; flag = 501; break;case(: wordsj = ch;wordsj+1 = 0;flag = 502; break;case):wordsj = ch; wordsj+1 = 0; flag = 503; break;case:wordsj = ch;wordsj+1 = 0;flag = 504;break;case:wordsj = ch; wordsj+1 = 0; flag = 505; break;case:wordsj = ch; wordsj+1 = 0;flag= 506;break;case:wordsj = ch;

13、 wordsj+1 = 0; flag = 507;break;case:wordsj = ch; wordsj+1 = 0; flag = 508;break;case:wordsj = ch;wordsj+1 = 0;flag = 509;break;case%:if (ch = %)wordsj+ = ch;wordsj = 0; ch = programi+;if (ch = =)wordsj+ = ch; wordsj = 0; flag= 510;elsei-;flag = 511;break;case,: wordsj = ch;wordsj+1 = 0; flag = 512;

14、 break;case#:wordsj = ch; wordsj+1 = 0; flag = 513; break;case: wordsj = #;flag = 0;break;case.:wordsj = ch; wordsj+1 = 0; flag = 514; break;case : wordsj = ; flag = 250;break;casen: flag = 251; break;default:flag = -1; break;return flag;main()i=0;printf(please input a program end with ); doch = getchar();programi+ = ch;w