浅谈C语言的scanf

#include<stdio.h>
int main() {
	float num,result;
	char tag;
	scanf("%f", &result);
	while (true)
	{
		tag = getchar();
		if (tag == '\n') {
			break;
		}
		else
		{
			scanf("%f", &num);
			switch (tag)
			{
			case '+':
				result += num;
				break;
			case '-':
				result -= num;
				break;
			case '*':
				result *= num;
				break;
			case '/':
				result /= num;
			}
		}
	}
	printf("%f", result);
}