设计程序计算的后缀表达式

#include <stdio.h>
#include <stdlib.h>
#define MAXSIZE 25
 typedef enum{OK=1,ERROR=0}Status;
 typedef double ElmType;
 typedef struct{
       ElmType data[MAXSIZE];
       int top;
 }SqStack;
 Status Push(SqStack* s, ElmType e) {
      if (s->top == MAXSIZE - 1) {
      return ERROR;//满
 }
      s->top++;
      s->data[s->top] = e;
      return OK;
 }
 ElmType Pop(SqStack* s, ElmType e) {
      if (s->top == -1) {
          return ERROR;//栈空
    }
      e = s->data[s->top];
      s->top--;
      return e;
 }
 ElmType com(char* zfc) {
       ElmType a, b, c, d, e=0;
       SqStack* s=(SqStack*)malloc(sizeof(SqStack));
       s->top = -1;
       while(*zfc!='\0'){
           switch (*zfc){
               case'+':{
                a= Pop(s, a);
                b= Pop(s, b);
                c = b + a;
                Push(s, c);
                break;
            }
            case'-':{
                a= Pop(s, a);
                b= Pop(s, b);
                c = b - a;
                Push(s, c);
                break;
            }
            case'*':{
                a= Pop(s, a);
                b= Pop(s, b);
                c = b * a;
                Push(s, c);
                break;
            }
            case'/':{
                a= Pop(s, a);
                b= Pop(s, b);
                if (a!= 0){
                    c = b/a;
                    Push(s, c);
                    break;
                }
                else{
                    printf("除零错误\n");
                    return ERROR;
                }
            }
            default:{
                while(*zfc>= '0' && '9'>=*zfc) {
                    d = *zfc-'0';
                    Push(s, d);
                    break;
                }    //while的
            }    //default的
        } // switch 的
        zfc++;
    } //while
    return Pop(s,e);
 }
int main() {
    ElmType a;
    char zfc[]="";
    gets(zfc);
    a=com(zfc);
    printf("表达式的值：%f\n", a);
    return 0;
 }