Error LNK2019

[gevCplus]

Hello guys once again. I would like to ask yuou a question regarding my following code. Despite the fact that visual studio states that no issues found, when I try to compile the code it reads
<<Severity Code Description Project File Line Suppression State
Error LNK2019 unresolved external symbol "public: __thiscall box::box(void)" (??0box@@QAE@XZ) referenced in function _main>> 1

Any ideas why this?

Thank you in advance!


//Headers
#include <iostream>
#include <string>
#include <cmath>
#include <algorithm>
#include <cstdio>

using namespace std;

class box {
private:
double x{};
double y{};
double z{};
public:
box();
box(double a, double b, double c) : x(a), y(b), z(c) {};
double volume() {
return x * y * z;
};
void set_xyz(double a, double b, double c) { x = a; y = b; z = c; };
double get_xyz() { return x; return y; return z; };
friend double perimeter(box &obj);
};

double perimeter(box &obj) {
return 4 * (obj.x + obj.y + obj.z);
}


int main()
{
box obj1;
obj1.set_xyz(2, 10, 2);
cout << perimeter(obj1) << endl;

return 0;
}

[lastchance]

You have declared - but never defined - a constructor taking zero parameters, as you will need in main().

Change
box();
to
box(){}
and your compiler, at least, will be happy.

Alternatively, you could remove that constructor and use default arguments in your other one.

[salem c]

Your default constructor needs an implementation.

box() : x(0), y(0), z(0) {};

And learn about code tags.
https://www.cplusplus.com/articles/jEywvCM9/

[gevCplus]

Guys, thank you very much for your replies. I am unacceptable by forgetting to define the constructor taking zero parameters! Thank you again.

@salem c: I know about the code tags I just forgot to set the tag. Thank you again.

[seeplus]

There is an issue with get_xyz(). This doesn't do what you trying to do. It will only return the value of x. To return values for x y z consider for C++17:

#include <iostream>
#include <tuple>

using namespace std;

class box {
	double x {};
	double y {};
	double z {};

public:
	box() noexcept =default;
	box(double a, double b, double c) noexcept : x(a), y(b), z(c) {}

	double volume() const noexcept { return x * y * z; };
	void set_xyz(double a, double b, double c) noexcept { x = a; y = b; z = c; };
	auto get_xyz() const noexcept { return tuple(x, y, z); }

	friend double perimeter(const box& obj) noexcept;
};

double perimeter(const box& obj) noexcept {
	return 4 * (obj.x + obj.y + obj.z);
}

int main()
{
	box obj1;

	obj1.set_xyz(2, 10, 2);
	cout << perimeter(obj1) << '\n';

	const auto [x, y, z] {obj1.get_xyz()};

	cout << "x = " << x << " y = " << y << " z = " << z << '\n';
}

56
x = 2 y = 10 z = 2