递归下降语法分析器源代码＃i nclude "stdio.h"＃i nclude "malloc.h"
void e();void f();void t();void t1();void e1();
struct Lchar{ char char_ch; struct Lchar *next;}Lchar,*p,*h,*temp;char ch;int right;
void e(void){ t(); e1();}
void t(void){ f(); t1();}
void t1(void){ if(h->char_ch=='*') { h=h->next; f(); t1(); } else if(h->char_ch!='#'&&h->char_ch!=')'&&h->char_ch!='+') right=0;}
void e1(void){ if(h->char_ch=='+') { h=h->next; t(); e1(); } else if(h->char_ch=='#'||h->char_ch==')') return; else right=0;}
void f(){ if(h->char_ch=='i') h=h->next; else if(h->char_ch=='(') { h=h->next; e(); if(h->char_ch==')') h=h->next; else right=0; } else right=0;}
void main(void){ right=1; h=malloc(sizeof(Lchar)); h->next=NULL; p=h; do{ ch=getch(); putch(ch); if(ch=='i'||ch=='+'||ch=='*'||ch=='('||ch==')'||ch=='#') { temp=malloc(sizeof(Lchar)); temp->next=NULL; temp->char_ch=ch; h->next=temp; h=h->next; } else { temp=p->next; printf("\nInput a wrong char!Input again:\n"); for(;;) { if (temp!=NULL) printf("%c",temp->char_ch); else break; temp=temp->next; } } }while(ch!='#'); p=p->next; h=p; e(); if(h->char_ch=='#'&&right) printf("\nOK!\n"); else printf("\nError!\n"); getchar();}
