I have Error in c++ when i write my code say : Error	1	error C2601: 'circle' : local function definitions are illegal : **i have problem inn c++ when i write this code
the vs say	error C2601: 'circle' : local function definitions are illegal**

*how can find solution for the problem*

    #include < iostream > 
        using namespace std;
        int main() {
        	char grade;
        	cout << "enter grade : ";
        	cin >> grade;
        	switch (grade) {
        	case 'A':
        		void circle(float &, float &, float);
        		{
        			float r, a, c;
        			cout << "enter radius:";
        			cin >> r;
        			circle(a, c, r);
        			cout << "area=" << a << "\t" << "circumference=" << c << endl;
        			return 0;
        		}
        		void circle(float & area, float & circumference, float r)
        		{
        			const double pi = 3.14159;
        			area = pi * r * r;
        			circumference = 2 * pi * r;
        		}
        		break;
        	default:
        		cout << "Invalid grade" << endl;
        	}
        	cout << "Your grade is " << grade << endl;
        
        	return 0;
        }