no matching function call error

Question

I'm trying to overload my << operator, but I want to use a helper function because I'm working with a tree, and that way my helper fn. can be recursive. But when I try to call the helper from the operator function I'm getting this no matching function call error.

std::ostream& operator<<(std::ostream& out, const Polynomial &rhs)
{
    Polynomial::Node *p = rhs.root;
    rhs.printPoly(p, out);
    return out;
}


void Polynomial::printPoly(Node* p, std::ostream &out)
{
    if(p == nullptr)
        return;
    printPoly(p->left, out);
    out << p->item->coeff() << "x^" << p->item->x();
    printPoly(p->right, out);
}

and in the .h file

friend std::ostream& operator<<(std::ostream& out, const Polynomial& rhs);

Oh and here's the error:

no matching function for call to 'Polynomial::printPoly(Polynomial::Node*&, std::ostream&) const'

score 2 · Accepted Answer · answered Nov 17 '13 at 20:03

2

Add const to the end of your function declaration:

void Polynomial::printPoly(Node* p, std::ostream &out) const
{
    ...
}

This extra const tells the compiler that you won't be modifying the Polynomial object in the printPoly method.

answered Nov 17 '13 at 20:03

godel9

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That was the first thing I tried, and it was still yelling at me. I'll try again. – Scuba Steve Nov 17 '13 at 20:04
@ScubaSteve Sorry, I had a typo. Just updated my post... Try again. – godel9 Nov 17 '13 at 20:05
Ah yeah thanks its working now. I like this solution better than mine. – Scuba Steve Nov 17 '13 at 20:06

score 0 · Answer 2 · answered Nov 17 '13 at 20:03

0

Ah I just ditched the const in the declaration of Polynomial &rhs, and it seems happy.

answered Nov 17 '13 at 20:03

Scuba Steve

1,541
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You actually want that `const`, since you're not modifying the object in the function. Adding `const` qualifiers where appropriate helps avoid undesired side-effects and helps with compiler optimization. – godel9 Nov 17 '13 at 20:12

no matching function call error

2 Answers2