C语言求文法的First集

1、C语言求文法的FIRST集/Copyright:ChenZexi , JXNU#include<string.h>#include<stdio.h>#include <stdlib.h>#define MAXS 50#define epsilon '*'char noendMAXS; /非终极符char EndMAXS; /终极符 int N;struct STRint has_epsion; char left; char rightMAXS;struct Firstchar letter;char gatherMAXS; ; int ge

2、tlr(struct STR *p,int i,char *temp) int j; int k=0; int succ=0; for(j=0;j<strlen(temp);j+) if(tempj='-' && tempj+1='>' ) succ=1; if(j=1) pi.left=temp0; j=3; pi.has_epsion=0; while(tempj!='0') pi.rightk=tempj; if(tempj=epsilon) pi.has_epsion=1; k+;j+; pi.rightk=&

3、#39;0' return succ;int findchar(char *s,char c)int i;int index=-1;for(i=0;i<strlen(s);i+)if(si=c) index=i; return index; int hasepsilon(struct STR *p,char c)int i;int index=-1;for(i=0;i<N;i+)if(pi.left=c && pi.has_epsion=1)index=1; return index; /求VN(终极符)和VT（非终极符） void VNVT(struct

4、STR *p) int i,j,x; for(i=0;i<N;i+) for(j=0;j<1;j+) if(pi.left >= 'A' && pi.left <= 'Z') if(findchar(noend,pi.left)<0) x=strlen(noend); noendx=pi.left; noendx+1='0' for(j=0;j<strlen(pi.right);j+) if(!(pi.rightj>='A'&&pi.rightj<=&

5、#39;Z') if(findchar(End,pi.rightj)<0) x=strlen(End); Endx=pi.rightj; Endx+1='0' else if(findchar(noend,pi.rightj)<0) x=strlen(noend); noendx=pi.rightj; noendx+1='0' /非终极符的FIRST集 void Firstgather(struct STR *p,struct First *f)int i,j,k,l,m;int x,n;int change=1; int eps;for(i

6、=0;i<strlen(noend);i+)strcpy(fi.gather,""); /清空缓存 /非终极符First集while(change=1)change=0;for(i=0;i<strlen(noend);i+)fi.letter=noendi;/扫描产生式 for(j=0;j<N;j+)if(pj.left=fi.letter)/查看是否是非终极符 n=findchar(noend,pj.right0);/不是非终极符 if(n<0)k=0;/直接收取：对形如U>a的产生式（其中a是终结符），把a收入到First(U)中 if(f

7、indchar(fi.gather,pj.rightk)<0) x=strlen(fi.gather); fi.gatherx=pj.rightk; fi.gatherx+1='0' change=1;/是非终极符 else/反复传送：对形入U>P的产生式（其中P是非终结符），应把First(P)中的全部内容传送到First(U)中for(l=0;l<strlen(pj.right);l+)/检测终极符 if(findchar(End,pj.rightl)>=0 && findchar(fi.gather,pj.rightl)<0)

8、x=strlen(fi.gather);fi.gatherx=pj.rightl; fi.gatherx+1='0' change=1;break;/左递归继续 if(pj.rightl=fi.letter) continue;/其他情况for(m=0;m<strlen(noend);m+)if(noendm=pj.rightl)for(k=0;k<strlen(fm.gather);k+)if( fm.gatherk!=epsilon && findchar(fi.gather,fm.gatherk)<0 ) x=strlen(fi.gath

9、er); fi.gatherx=fm.gatherk; fi.gatherx+1='0' change=1;if(hasepsilon(p,pj.rightl)<0) break;if(l=strlen(pj.right)-1 && findchar(fi.gather,epsilon)<0) x=strlen(fi.gather); fi.gatherx=epsilon; fi.gatherx+1='0' change=1; void printFirst(struct First *f)int j,k;printf("非

10、终极符的FIRST集n"); for(j=0;j<strlen(noend);j+) /printf("%s n",fj.gather); printf("FIRST(%c)=",fj.letter); for(k=0;k<strlen(fj.gather);k+)printf("%c",fj.gatherk); if(k<strlen(fj.gather)-1)printf(",");printf("n"); void printProduction(struct

11、STR *p,int i) int j,k; printf("序号 产生式：n"); for(j=0;j<i;j+) printf(" %2d %c -> %s n",j,pj.left,pj.right); printf("非终极符集合：nVT=");for(j=0;j<strlen(noend);j+)printf("%c",noendj); if(j<strlen(noend)-1)printf(",");printf("n");printf(&

12、quot;终极符集合：nVN=");for(j=0;j<strlen(End);j+)printf("%c",Endj); if(j<strlen(End)-1)printf(",");printf("n");/主函数int main()int i;int jMAXS; struct STR pMAXS;struct First fMAXS; char tempMAXS; do printf("请输入产生式数目n"); scanf("%d",&N); getchar(); while(N<=0); pri