带有数学问题的 c++ 函数

Question

I'm starting learning c++ and stepped on this problem, trying to make the following calculation: place + (place / 10)² which if place = 90 it should be 171.

    #include <iostream>
    #include <iomanip>
    #include <cmath>
    #include "TestFunction.h"

    using namespace std;

    int main() {
        TestFunction test1 ("John", 90);
        test1.getInfo();
    }

here is the TestFunction header

#include <iostream>
#include <string>
#include <iomanip>

class TestFunction {

public:
    TestFunction(std::string userName, int userPlace) {
        name = userName;
        place = userPlace;
    }

    int getPlace() {
        return place;
    }

    int getResult() {
        return num1;
    }

    void getInfo() {
        std::cout << "Using getPlace():" << getPlace() << std::endl;
        std::cout << "Using getResult(): " << getResult() << std::endl;
        std::cout << "Using num1: " << num1 << std::endl;
        std::cout << "calculate here: " << getPlace() + pow(getPlace() / 10, 2) << std::endl;
    }

private:
    std::string name;
    int place;
    int num1 = place + pow(place / 10, 2);
};

and get this result:

Using getPlace():90
Using getResult(): -2147483648
Using num1: -2147483648
calculate here: 171

I really don't know what I am missing when trying to use getResult() or num1, any advice or simple explanation will be welcome, thanks.

Answer 1

You need to keep track of when your calculations are done.
The init of num1 is done earlier than the initialisation of place , which is something to avoid at all cost.
You could move that calculation into the constructor:

TestFunction(std::string userName, int userPlace) {
        name = userName;
        place = userPlace;
        num1 = place + pow(place / 10, 2);
    }

There are other ways, but this is probably most accessable to you.