Default constructor with no inputs - c++

Question

I am trying to create a class which has a constructor with no input arguments - I was trying to test it by printing to the screen. However unless I give the constructor an input the constructor gets skipped straight over - the debug mode doesn't even register it as a line - can anyone shed light on this?
Also, is it possible to call the constructor of another class from inside a constructor/function belonging to a different class?
Header file:
#pragma once
#include <vector>
using namespace std;
class rain
{
public:
rain();
void update();
~rain();
private:
};
Source file:
#include "stdafx.h"
#include "rain.h"
#include "Digital Rain.h"
#include "Stream.h"
#include <Windows.h>
#include <iostream>
#include "Stream.h"
using namespace std;
int screen_width = 79;
rain::rain()
{
cout << "hi" << endl;
}
void rain::update()
{
Sleep(5);
}
rain::~rain()
{
}

Answer 1

Let's look at a piece of code:
#include <iostream>
class rain {
public:
rain();
};
rain::rain() {
std::cout << "hi\n";
}
int main() {
rain x();
rain y;
}
When we run this, we'll see hi on the output only once. This is because of the Most Vexing Parse.
So:
x is actually a function declaration for a function that takes no arguments and returns a rain object.
y is actually a rain object.
Additionally, your compiler might warn you about this situation. clang for example will report:
asdd.cc:26:11: warning: empty parentheses interpreted as a function declaration [-Wvexing-parse]
rain x();
^~
asdd.cc:26:11: note: remove parentheses to declare a variable
rain x();
^~
1 warning generated.