编译原理实验递归下降语法分析

1、递归下降语法分析姓名：郝梦朔 学号：71107416 日期：2010-1-17一、 实验目的构造文法的语法分析程序，要求采用递归下降语法分析方法对输入的字符串进行语法分析，实现对词法分析程序所提供的单词序列的语法检查和结构分析，进一步掌握递归下降的语法分析方法。二、 实验内容编写为一上下文无关文法构造其递归下降语法分析程序，并对任给的一个输入串进行语法分析检查。程序要求能对输入串进行递归下降语法分析，能判别程序是否符合已知的语法规则，如果不符合（编译出错），则输出错误信息。三、 实验要求利用c语言编制递归下降分析程序，并对语言进行语法分析。（1） 待分析的语言的语法。用扩充额bnf表示如下。&

2、lt;程序>:=function<语言串>endfunc<语言串>:=<语句><语句><语句>:=<赋值语句><赋值语句>:=id=<表达式><表达式>:=<项>+<项>|-<项><项>:=<因子>*<因子>|/<因子><因子>:=id|num|(<表达式>)（2） 实验要求说明输入单词串以“#”结束，如果是文法正确的句子，则输出成功信息，打印“success”，否则输出“e

3、rror”，具体例子如下。输入functiona=9;x=2*3;b=a+x;endfunc#输出success又如，输入：x=a+b*cendfunc#输出error（3）语法分析程序的算法思想为翟玉庆老师上课所讲。四、 实验源程序#include<stdio.h>#include<string.h>char prog80,token8;char ch;int syn,p,m=0,n,sum,kk=0;char *rwtab6="function","if","then","while",

4、"do","endfunc"void scaner();void lrparser();void yucu();void statement();void expression();void term();void factor();void main()p = 0;printf("please input the string:n");doch = getchar();progp+ = ch;while(ch != '#');p = 0;ch = progp+;scaner();lrparser();return;v

5、oid scaner()for(n=0;n<8;n+)tokenn=null;/printf("n%c in scaner()",ch);while(ch = ' ' | ch = 'n' )ch = progp+;/printf("n%c in scaner()",ch);m = 0;if(ch<='z' && ch>='a') |(ch<='z' && ch>='a')while(ch<=

6、'z' && ch>='a') |(ch<='z' && ch>='a')|(ch<='9' && ch>='0')tokenm+ = ch;ch = progp+;syn=10;for(n=0;n<6;n+)if(strcmp(token,rwtabn) = 0)syn = n+1;/printf("n%d in keyword",syn);break;tokenm+ = '0'

7、else if(ch<='9' && ch>='0')sum=0;while(ch<='9' && ch>='0')sum = sum*10 + ch - '0'ch = progp+;syn = 11;elseswitch(ch)case '<':m = 0;tokenm+ = ch;ch = prog+p;if(ch = '=')syn = 22;tokenm+ = ch;elsesyn = 20;ch = prog-

8、p;break;case '>':m = 0;tokenm+ = ch;ch = prog+p;if(ch = '=')syn = 24;tokenm+ = ch;elsesyn = 23;ch = prog-p;break;case '=':m = 0;tokenm+ = ch;ch = prog+p;if(ch = '=')syn = 25;tokenm+ = ch;elsesyn = 18;ch = prog-p;break;case '!':m = 0;tokenm+ = ch;ch = prog+p

9、;if(ch = '=')syn = 22;tokenm+ = ch;elsesyn = -1;break;case '+':syn = 13;token0 = ch;break;case '-':syn = 14;token0 = ch;break;case '*':syn = 15;token0 = ch;break;case '/':syn = 16;token0 = ch;break;case '':syn = 26;token0 = ch;break;case '(':sy

10、n = 27;token0 = ch;break;case ')':syn = 28;token0 = ch;break;case '#':syn = 0;token0 = ch;break;default:syn = -1;ch = progp+;void lrparser()if(syn =1)/printf("n%d",syn);scaner();/printf("n%d",syn);yucu();/*/printf("n%d after yucu()",syn);if(syn = 6)scane

11、r();/printf("n%d in lrparser() after scaner()",syn);if(syn = 0 && kk = 0)printf("nsuccess!n");elseif(kk != 1)printf("error!need 'endfunc'");kk = 1;elseprintf("error!need 'function'");kk =1;return;void yucu()/printf("n%d in yucu() f

12、irst",syn);statement();/printf("n%d after statement() in yucu()",syn);while(syn = 26)scaner();/syn = 6;/printf("n%d after scaner() in yucu()",syn);statement();return;void statement()/printf("n%d in statement() at first",syn);if(syn = 10)scaner();/printf("n%d a

13、fter scaner() in statement()",syn);if(syn = 18)scaner();/printf("n%d after scaner when syn=18",syn);expression();/printf("n%d after expression()",syn);elseprintf("error! evaluate tag error");kk = 1;else if(syn = 6)return;else printf("error! the statement error

14、!");kk = 1;return;void expression()/printf("n%d in expression at first",syn);term();while(syn = 13 | syn = 14)scaner();term();return;void term()/printf("n%d in term() at first",syn);factor();while(syn = 15 | syn = 16)scaner();factor();return;void factor()/printf("n%d in factor() at first",syn);if(syn = 10 | syn = 11)scaner();elseif(syn = 27)scaner();expression();if(syn