栈的应用——四则表达式

#include <stdio.h>

#define MAX 100

struct operand
{
    int data[MAX];
    int top;
};

struct operator_ch
{
    int top;
    char data[MAX];
};


typedef struct operand OPND;
typedef struct operator_ch OPCH;

void init_OPND_stack(OPND *stack)
{
	stack->top = -1;
}

void init_OPCH_stack(OPCH *stack)
{
	stack->top = -1;
}

void is_empty_OPND(OPND *stack)
{
	if(stack->top == -1)
	{
		return -1;
	}

	return 0;
}

void is_empty_OPCH(OPCH *stack)
{
	if(stack->top == -1)
	{
		return -1;
	}

	return 0;
}

int get_OPND_top(OPND *stack)
{
	if(is_empty_OPND(stack) == -1)
	{
		return -1;
	}

	return stack->data[stack->top];
}

int get_OPCH_top(OPCH *stack)
{
	if(is_empty_OPCH(stack) == -1)
	{
		return -1;
	}

	return stack->data[stack->top];
}

int push_OPND(OPND *stack, int num)
{
    stack->data[++(stack->top)] = num;
}

int push_OPCH(OPND *stack, char ch)
{
    stack->data[++(stack->top)] = ch;
}

int pop_OPND(OPND *stack)
{
	if(is_empty_OPND(stack) == -1)
	{
		return -1;
	}
    
	int num = stack->data[stack->top];

	(stack->top)--;

	return num;
} 

char pop_OPCH(OPCH *stack)
{
	if(is_empty_OPCH(stack) == -1)
	{
		return -1;
	}
    
	char ch = stack->data[stack->top];

	(stack->top)--;

	return ch;
} 

int get_priority(char ch)
{
	if(ch == '+' || ch == '-')
	{
		return 1;
	}

	if(ch == '*' || ch == '/')
	{
		return 2;
	}
}

int compare_priority(char op_ch, char ch)
{
	if(get_priority(op_ch) > get_priority(ch))
	{
		return 1;
	}
	
	return -1;
}

int count(int num1, int num2, char ch)
{
    int result;

	switch(ch)
	{
		case '+':
		{
            result = a + b;
			break;
		}

		case '-':
		{
			result = a - b;
			break;
		}
		
		case '*': 2
		{
			result = a * b;
			break;
		}
		
		case '-':
		{
			result = a / b;
			break;
		}
	}

	return result;
}

int main()
{
    char ch;
	char op_ch;

	while((ch = getchar()) != '\n')
	{
        if(ch >= '0' && ch <= '9')
		{
            push_stack1();
		}

		if(ch == '+' || ch == '-' || ch == '*' || ch == '/')
		{
			op_ch = pop_stack2();
			if(compare(op_ch,ch) > 0)
			{
				push_stack2(ch);
			}
			else
			{
				count(a,b,op_ch);
			}
		}
	}
	
	return 0;
}