rpn_calculator for exam

calc.c

#include "rpn_calc.h"

int		is_op(char *str)
{
	if (*str == '+' || *str == '-' || *str == '/' || *str == '*' || *str == '%')
	{
		if (*(str + 1) && *(str + 1) != ' ')
			return (0);
		else
			return (1);
	}
	return (0);
}

int		is_numeric(char *str)
{
	if (*str == '-')
		++str;
	while (*str && *str != ' ')
	{
		if (*str >= '0' && *str <= '9')
			++str;
		else
			return (0);
	}
	return (1);
}

int		ft_calc(int	a, int b, char op)
{
	if (op == '+')
		return (a + b);
	else if (op == '-')
		return (a - b);
	else if (op == '/')
		return (a / b);
	else if (op == '*')
		return (a * b);
	else if (op == '%')
		return (a % b);
	return (0);
}

void	rpn_calculate(char *str)
{
	int		nums[256];
	int		num_vals;
	int		ix;

	ix = 0;
	num_vals = 0;
	while (str[ix])
	{
		if (is_op(&str[ix]))
		{
			if (num_vals >= 2)
			{
				if (nums[num_vals - 1] == 0 && (str[ix] == '/' || str[ix] == '%'))
				{
					printf("Error\n");
					return ;
				}
				nums[num_vals - 2] = ft_calc(nums[num_vals - 2], nums[num_vals - 1], str[ix]);
				--num_vals;
				if (str[ix + 1])
					ix += 2;
				else
					break ;
			}
			else
			{
				printf("Error\n");
				return ;
			}
		}
		else if (is_numeric(&str[ix]))
		{
			nums[num_vals++] = atoi(&str[ix]);
			while (str[ix] && str[ix] != ' ')
				++ix;
			if (str[ix])
				++ix;
		}
		else
		{
			printf("Error\n");
			return ;
		}
	}
	if (num_vals == 1)
		printf("%d\n", nums[0]);
	else
		printf("Error\n");
}

main.c

#include "rpn_calc.h"

int		main(int argc, char **argv)
{
	if (argc == 2)
		rpn_calculate(argv[1]);
	else
		printf("Error\n");
}

rpn_calc.h

#include <stdlib.h>
#include <stdio.h>

void	rpn_calculate(char *str);