Using an overloaded operator+ within a function template in C++ - c++

Question

This is for a school assignment. I am supposed to adhere to the requirement to use an overloaded operator and it has to be called within the function template called "increase".
This is a class called Inductor.
#pragma once
#include <iostream>
using namespace std;
class Inductor {
friend ostream& operator<<(ostream&, Inductor);
private:
int inductance;
double maxCurrent;
public:
int operator+(int add);
int operator-(int sub);
Inductor(int, double);
};
Inductor::Inductor(int x, double y)
{
inductance = x;
maxCurrent = y;
}
int Inductor::operator+(int add)
{
int newSum = inductance + add;
return newSum;
}
int Inductor::operator-(int sub)
{
int newDiff = inductance - sub;
return newDiff;
}
ostream& operator<<(ostream& out, Inductor inductor)
{
out << "Inductor parameters: " << inductor.inductance << ", " << inductor.maxCurrent << endl;
return out;
}
While this is my function template "increase".
template<class FIRST>
FIRST increase(FIRST a, int b) {
FIRST c;
c = a + b;
return c;
}
Last but not least, my main file:
int main()
{
Inductor ind(450, 0.5);
ind = increase(ind, 70);
}
These are the following compilation errors which I do not understand:
error C2512: 'Inductor': no appropriate default constructor available
error C2679: binary '=': no operator found which takes a right-hand operand of type 'int' (or there is no acceptable conversion)
note: could be 'Inductor &Inductor::operator =(Inductor &&)'
note: or 'Inductor &Inductor::operator =(const Inductor &)'
note: see reference to function template instantiation 'FIRST increase<Inductor>(FIRST,int)' being compiled
with
[
FIRST=Inductor
]
note: see declaration of 'Inductor'
Can anyone care to explain why is the compiler throwing these errors? Yes I have googled and searched through StackOverflow, but I do not see an article where an overloaded operator+ from a class is being used within a function template.

Answer 1

template<class FIRST>
FIRST increase(FIRST a, int b) {
FIRST c;
c = a + b;
return c;
}
with FIRST == Inductor has several problems:
FIRST c;: You try to create Inductor whereas there is no default constructor.
c = a + b;: You try to assign to Inductor an int (return type of your operator +), and there is no such operator. and as there is no constructor taking only int to build Inductor, copy assignment is not an alternative.
The first error is easy to fix, just get rid of the variable (return a + b;) or initialize it directly (FIRST c = a + b; return c;).
For the second error, add a (non explicit) constructor taking only an int or change your operator+ to return Inductor directly:
Inductor Inductor::operator+(int add)
{
return Inductor(inductance + add, maxCurrent);
}