Basic Shape class and Circle Class: compiling error - c++

Question

I have this homework assignment to do and I did most of the code, but I have a remaining compiling error in main(), that I do not understand.
Here's the assignment:
Define an abstract base class called BasicShape. The BasicShape class should have the following members (...)
Define a class named Circle. It should be derived from the BasicShape class.
It should have the following members:
a) Private Member Variable: radius (a double used to hold the circle’s
radius)
b) Constructor and Public Member Functions:
Circle(double a, string
n, double r): constructor that should call the base class constructor
to initialize the member area with a and name with n. The constructor
will also set the value of member radius with r
calcArea():
Overridden function (...)
print(): Overridden function (...)
After you have created these classes, create a test program
(...)
And here's my code:
Basic Shape.h
#ifndef BASICSHAPE_H
#define BASICSHAPE_H
#include <string>
class basicShape
{
public:
basicShape(const std::string &, double &);
double getArea() const;
virtual double calcArea() const = 0;
virtual void print()const;
std::string getname()const;
protected:
const double area;
private:
const std::string name;
};
#endif
Circle.h
#ifndef CIRCLE_H
#define CIRCLE_H
#include <string>
#include "Basic Shape.h"
using namespace std;
class Circle : public basicShape
{
public:
Circle(const string & n, double & a, double & r);
virtual double calcArea() const override;
virtual void print() const override;
private:
double radius;
};
#endif
Circle.cpp
#include <iostream>
#include "Circle.h"
#include<string>
using namespace std;
Circle::Circle(const string &n, double &a, double &r)
:basicShape(n,a)
{
radius = r;
calcArea();
}
double Circle::calcArea() const
{
double area;
area = 3.14159*radius*radius;
return area;
}
double basicShape::getArea() const
{
return area;
}
void Circle::print() const
{
cout << "radius:" << radius;
basicShape::print();
basicShape::getname();
}
Test.cpp
#include <iostream>
#include "Basic Shape.h"
#include "Circle.h"
#include <string>
#include<vector>
using namespace std;
void poly(const basicShape * const);
int main()
{
Circle circle("Round",0.0,10.0);
vector< basicShape * > shapes(1);
for (const basicShape *basicshapePtr : shapes)
poly(basicshapePtr);
}
void poly(const basicShape * const baseClassPtr)
{
baseClassPtr->calcArea();
baseClassPtr->print();
}
Here is the compiling error I get in main:
"Circle::Circle(Circle Assignment 3 &&)': cannot convert argument 2 from 'double' to 'double &'

Answer 1

The problem
You try to construct your new circle here:
Circle circle("Round",0.0,10.0);
But your constructor has the following signature:
Circle(const string &n, double &a, double &r)
For the second and third arguments you use references to double values. Passing by reference like this means that you could change the value that is referenced. Unfortunately, you pass constant literals. This is not allowed.
The solution
Either define your constructor by using const references:
Circle(const string &n, const double &a, const double &r)
or, pass by value:
Circle(string n, double a, double r)
Note that the second option seems preferred here. And I'd even advise you to respect the signature given in the assignment, which would have avoided you those troubles.
P.S.: For future questions, please reduce the question to the minimal elements required to reproduce the errors, instead of posting the full assignment and the full code, most of which being not relevant to the error