词法分析器实验报告

1、实验报告实验题目：词法分析器 院系班级：计科系0901班 姓名学号： 2009210603实验时间：2011-10-21 实验目的设计。编制并调试一个词法分析程序，加深对词法分析原理的理解。实验要求设计出一个简单的词法分析程序，能够识别关键字（包含begin、if、end、 while、else、 then）、标识符、数字及数种符号（+、-、*、/、（、）、：、=、：=、#、>、<、<>、<=、>=、；）。返回并打印各类字符所对应的种类编码及该字符所组成的二元组。算法设计流程图源代码 # include <stdio.h> # include &

2、lt;string.h> # include <stdlib.h> # include <ctype.h> typedef struct int num; char *word; WORD; char token255="" char input255; int t=0; int i=0; char gjz610="begin","if","then","while","do","end" char ch; WORD* sta

3、rt() WORD*myword=new WORD; myword->num=1; myword->word="" t=0;ch=inputi;i+;while(ch=' '|ch=10)ch=inputi; i+;if (isalpha(ch) while(isalpha(ch)|isdigit(ch) tokent=ch; t+; tokent='0' ch=inputi; i+; i-; int n=0; while(n<=6) if(!strcmp(token,gjzn) myword->num=n+1; my

4、word->word=token; return myword; n+; /关键字 myword->num=10; myword->word=token; return(myword);/标识符else if(isdigit(ch) while (isdigit(ch) tokent=ch; t+; tokent='0' ch=inputi; i+; i-; myword->num=11; myword->word=token; return(myword); /数字elseswitch(ch) case'+':myword->

5、;num=13; myword->word="+" return(myword);break; case'-':myword->num=14; myword->word="-" return(myword);break; case'*':myword->num=15; myword->word="*" return(myword);break; case'/':myword->num=16; myword->word="/"

6、return(myword);break; case'<':ch=inputi; i+; if(ch='>') myword->num=21; myword->word="<>" return(myword); else if (ch='=') myword->num=22; myword->word="<=" return(myword); i-; myword->num=20; myword->word="<"

7、return(myword);break; case'>':ch=inputi; i+; if(ch='=') myword->num=24; myword->word=">=" return(myword); i-; myword->num=23; myword->word=">" return(myword);break; case':':ch=inputi; i+; if (ch='=') myword->num=18; myword-&

8、gt;word=":=" return(myword); i-; myword->num=17; myword->word=":" return(myword); break; case'':myword->num=26; myword->word="" return(myword);break; case'(':myword->num=27; myword->word="(" return(myword);break; case')

9、9;:myword->num=28; myword->word=")" return(myword);break; case'=':myword->num=27; myword->word="=" return(myword);break; case'#':myword->num=0; myword->word="#"break; case'0':myword->num=1000; myword->word="OVER"break; default: myword->num=-1; myword->word="error" return(myword);break;/符号 void main() WORD* newword=new WORD; printf("input your words:(end with #)n"); scanf("%#s",input); while(newword->num!=1000) newword=start();pr