КМБО-07-23 калькулятор со string

calcstr.cpp

#include <cmath>
#include <cstdlib>
#include <iostream>

using namespace std;

float calc(string op, float x, float y);

int main() {
    float x, y, res;
    char op, c = '1', arr[] = "123456789";
    string ops;
    cout << "Enter x: ";
    cin >> x;
    cout << "Enter operation: ";
    cin >> ops;
    cout << "Enter y: ";
    cin >> y;
    res = calc(ops, x, y);
    cout << "x " << ops << " y = " << res << endl;
    return 0;
}

float calc(string op, float x, float y) {
    float res;

         if (op == "+")
        res = x + y;
    else if (op == "-")
        res = x - y;
    else if (op == "*")
        res = x * y;
    else if (op == "/")
        res = x / y;
    else if (op == "ln")
        res = log(x) / log(y);
    else {
        cerr << "Unsupported operation: '" << op << "'\n";
        exit(1);
    }
    return res;
}