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 # include # include # include typedef struct int num; ch

2、ar *word; WORD; char token255=; char input255; int t=0; int i=0; char gjz610=begin,if,then,while,do,end; char ch; WORD* start() 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=

3、inputi; i+; i-; int n=0; while(nnum=n+1; myword-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

4、-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=/; return(myword);break; case) myword-num=21; myword-word=; return(myword); else if (ch=) myword-num=22;

5、myword-word=num=20; myword-word=: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-word=:=; return(myword); i-; myword-num=17; myword-word=:; return(myword); break; case;:mywor

6、d-num=26; myword-word=; return(myword);break; case(:myword-num=27; myword-word=(; return(myword);break; case):myword-num=28; myword-word=); return(myword);break; case=:myword-num=27; myword-word=; return(myword);break; case#:myword-num=0; myword-word=#;break; case0: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();printf(%d,%s) ,newword-num,ne