栈的一些初始函数

#defin maxsize 1024

typedef struct
{
 datatype data[maxsize];
 int top;
}seqstack;
void SETNULL(seqstack *s)//置空栈
{
 s->top=-1;
}

void PUSH(seqstack *s,datatype x)//元素入栈
{
 if(s->top==maxsize-1)
  {
  printf("overflow");
  }
 else 
 {
  s->top++;
  s->data[s->top]=x;
 }
}

int EMPTY(seqstack *s)//判断栈空
{
 if(s->top>=0)return 0;
 else return 1;
}

int FULL(seqstack *s)//判断栈满
{
 if(s->top==maxsize-1)return 1;
 else return 0;
}

datatype POP(seqstack *s)//出栈,并返回当前栈顶元素
{
 if(EMPTY(s))
 {printf("underflow");}
 else 
 {
  s->top--;
                  return s->data[s->top];
 }
}

datatype TOP(seqstack *s)//返回栈顶元素
{
 if(EMPTY(s))
 {
  printf("stack is empty");return NULL;
 }
 else return (s->data[s->top]);
}