Initializing values for a struct within a class

Question

I have the following code in the private section of a basic Polynomial class .h file:

private:
struct Term
{
    float coefficient;
    int power; // power of specific term
};
int degree; //total number of terms

I have the following default constructor for the Polynomial class:

Polynomial::Polynomial()
{
    Polynomial.Term poly;
    poly.power = 0;
    poly.coefficient = 0;
    degree = 1;
}

I am confused on how to access the terms inside the struct as well as the variable outside the struct. I tried to google this, but couldn't find anything helpful.

Edit: overloaded output operator code

ostream & operator << (ostream & outs, Polynomial & P)
{
    outs << P[0].poly.coefficient << "x^" << P[0].poly.power;
    for (int i=1; i<P.degree-1; i++)
    {
        if (P[i].poly.coefficient > 0)
            outs << "+";
        outs << P[i].poly.coefficient << "x^" << P[i].poly.power;
    }
    outs << endl;
}

that is a variable I initialized using Term, trying to access the variables in Term. — Julie Rosen
– Julie Rosen, Commented Nov 21, 2017 at 4:23
The rest of the code isn't really relevant. I am just trying to figure out how to access the terms in the Term struct in the default constructor. What code are you asking for? — Julie Rosen
– Julie Rosen, Commented Nov 21, 2017 at 4:25

Grant Peters · Accepted Answer · 2017-11-21 04:25:34Z

5

You've declared the variable within the constructor function. Once execution leaves the constructor, that variable is destroyed. Instead, you need to add the variable to the class declaration. If you want to be able to access the members from outside any of the class functions, you'll also need to make the variables and struct definition public.

class Polynomial
{
public:
   struct Term
   {
      float coefficient;
      int power; // power of specific term
   };
   Term poly;
   int degree; //total number of terms

   Polynomial();
};

Polynomial::Polynomial()
{
    poly.power = 0;
    poly.coefficient = 0;
    degree = 1;
}

answered Nov 21, 2017 at 4:25

Grant Peters

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4 Comments

Julie Rosen Over a year ago

thank you very much. Now when overloading the output operator, I'm having trouble accessing power and coefficient. code updated in post

user1118321 Over a year ago

@JulieRosen - That sounds like a different problem. You should post a new question about that.

Grant Peters Over a year ago

@JulieRosen Yeah, that's a different issue, but as a quick hint: Your "P" variable in that function isn't an array. It looks like what you want is for the "poly" variable to be an array. e.g. Term poly[100]; Then you need to index 'poly', e.g. P.poly[i]

Grant Peters Over a year ago

Bonus tip, an "std::vector<Term>" is probably more appropriate for this data, rather than using "degree".

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