Question

getting error: neljastest.cpp: undefined reference to Vector2::Vector2(float, float)

neljastest.cpp:

    #include <cstdlib>
#include <iostream>
#include "../include/Vector2.h"
#include "../include/neljas.h"

using namespace std;

int main (int argc, char* argv[]) {
     Vector2 p1 (1.0, 2.0);
     Vector2 p2 (0.0, 0.0);
     Vector2 p3 (5.0, 2.0);
    return EXIT_SUCCESS;
}

vector2.h:

#ifndef VECTOR2_H
#define VECTOR2_H

#include <iostream>
using std::ostream;

class Vector2 {

public:
    float x;
    float y;

    Vector2();

    Vector2(float nx, float ny);

    float distanceFrom(Vector2 v);


};


ostream& operator << (ostream& valja, Vector2 v);

#endif

vector2.cpp:

    #include "../include/Vector2.h"
#include <cmath>

using namespace std;

Vector2::Vector2() {
    x = 0;
    y = 0;
}

Vector2::Vector2(float nx, float ny) {
    x = nx;
    y = ny;
}

float Vector2::distanceFrom(Vector2 v) {
    return sqrt( (x - v.x)*(x - v.x) + (y - v.y)*(y - v.y) );
}

ostream& operator << (ostream& os, Vector2 v) {
    return os << "(" << v.x << "," << v.y << ")";
}

Answer 1

C/C++ are case sensitive for headers too.

It seems that on vector2.cpp and neljastest.cpp you must change the include from:

#include "../include/Vector2.h"

To:

#include "../include/vector2.h"

I pasted all your sources on the same folder and successfully compiled them with:

g++ neljastest.cpp vector2.cpp -o neljastest

Edit:

Your problem is that the linking process of neljastest.cpp depends on src/vector2.cpp, and you are not doing that on the Makefile