Simple C++ program error c2064: term does not evaluate to a function taking 0 arguments

Question

New user, new to programming, x seconds of search didn't find me an answer. Whole code (incomplete - and an online quiz for basic stuff):

#include "stdafx.h"
#include <iostream>
#include "constant.h"

double towerheight()
{
    std::cout << "Input tower height" << std::endl;
    double height;
    std::cin >> height;

    return height;
}

double ballheight(double towerheight)
{
        //valid stuff goes here in program, but not applicable to question
}

int main()
{
    double towerheight;
    towerheight = towerheight();       //Error occurs here
    ballheight(towerheight);

    return 0;

}

3 lines from bottom ignoring whitespace and closing bracket is where the error occurs. (term does not evaluate to a function taking 0 arguments.)

I'm sort of lost at the research end of this and could use some human help.

Apologies for potentially poor formatting. Please advise, I may not know certain terms responsible for the error, and my goal is to understand what's going on.

EDIT:

Solution for me was changing the name of the double variable above the error. Why did this become an issue?

Answer 1

In main, the variable named towerheight shadows the function towerheight. Hence,

towerheight = towerheight(); 

is not valid. It is analogous to calling a function on a variable.

double towerheight;
double dummy;
towerheight = dummy();

That's why it is not correct.

Solution 1

You can use:

double towerheight;
towerheight = ::towerheight();

Using ::towerheight works since it refers to the name in the enclosing namespace and not the locally defined variable of the same name.

Solution 2

Use different names.

You can avoid some of the confusion by using two different names.

double t_height = towerheight();