是一个用栈解决表达式求职的问题，用两个栈存储运算符合运算数，输入一个表达式，比如：2+3*4-1，则输出13，我编的这个总是出错，各位帮忙看一下啊

#include <stdio.h>
#include <alloc.h>
#include <stdlib.h>
#define STACK_SIZE 40
#define STACKINCREMENT 10
typedef struct
{
    char *base;
    char *top;
    int stacksize;
}SqStack;
typedef struct
{
    int *base;
    int *top;
    int stacksize;
}SqStack_Num;

void InitStack(SqStack *s)
{
    s->base=(char *)malloc(STACK_SIZE*sizeof(char));
    if(!s->base)  exit(0);
    s->top=s->base;                    /*栈顶指向空*/
    s->stacksize=STACK_SIZE;
}

void InitStack_Num(SqStack_Num *s)
{
    s->base=(int *)malloc(STACK_SIZE*sizeof(int));
    if(!s->base)  exit(0);
    s->top=s->base;                    /*栈顶指向空*/
    s->stacksize=STACK_SIZE;
}

char GetTop(SqStack *s)
{
    if(s->top==s->base)  exit(0);
    return *(s->top-1);
}

int GetTop_Num(SqStack_Num *s)
{
    if(s->top==s->base)  exit(0);
    return *(s->top-1);
}

void Push(SqStack *s, char e)
{
    *(s->top)=e;
    s->top++;
}    

void Push_Num(SqStack_Num *s, int e)
{
    *(s->top)=e;
    s->top++;
}    

char Pop(SqStack *s)
{
    if(s->base==s->top)  exit(0);
    s->top--;
    return *(s->top);
}

int Pop_Num(SqStack_Num *s)
{
    if(s->base==s->top)  exit(0);
    s->top--;
    return *(s->top);
}

int In(char e)
{
    if(e>=48&&e<=57) return 0;
    else return 1;
}    

char Precede(char c,char d)
{
    int i,j;
    char a[7]={'+','-','*','/','(',')','#'};
    char b[7][7]={{'>','>','<','<','<','>','>'},
                  {'>','>','<','<','<','>','>'},
                  {'>','>','>','>','<','>','>'},
                  {'>','>','>','>','<','>','>'},
                  {'<','<','<','<','<','=',' '},
                  {'>','>','>','>',' ','>','>'},
                  {'<','<','<','<','<',' ','='}};
    for(i=0;c!=a[i];i++);
    for(j=0;d!=a[j];j++);
    return (b[i][j]);
}    

int Operate(int x,char c,int y)
{
    switch(c)
    {
        case'+':return (x+y);
        case'-':return (x-y);
        case'*':return (x*y);
        case'/':return (x/y);
    }    
}

char EvaluateExpression()
{
    SqStack *OPTR;
    SqStack_Num *OPND;
    char c,theta;
    char letter[20];
    int x,y;
    
    InitStack(OPTR);                      
    Push(OPTR,'#');      
    InitStack_Num(OPND);
    c=getchar();
    while(c!='#'||GetTop(OPTR)!='#')
      {
          if(!In(c))                            
            {
                Push(OPND,(int)(c-48));
                c=getchar();  
             }
          else
            switch(Precede(GetTop(OPTR),c))  
              {
                  case'<':Push(OPTR,c);c=getchar();break;
                  case'=':Pop(OPTR);c=getchar();break;
                  case'>':theta=Pop(OPTR);
                                        y=Pop_Num(OPND);x=Pop_Num(OPND);
                          Push_Num(OPND,Operate(x,theta,y));
                          if(c=='#') break;
                          else {Push(OPTR,c);
                                              c=getchar();break;}  
               }
       }    
     return(GetTop_Num(OPND));
}          

main()
{
    printf("%d",EvaluateExpression());   
}