Use function pointer in template class

Question

This is a selection of my class

template <typename TValue, typename TPred = std::less<TValue> >
class BinarySearchTree {
public:
BinarySearchTree<TValue, TPred> &operator=(BinarySearchTree<TValue, TPred> const &tree) {
    if (this != &tree) {
        tree.VisitInOrder(Insert);
    }
    return *this;
}
bool Insert(TValue const &value) {
    return m_Insert(value, pRoot);
}
template <typename TVisitor> void VisitInOrder(TVisitor visitor) const;
...
};

and the following sequence wont work: VisitInOrder(Insert) because my compiler says that there are arguments missing

but my main looks like this and there i can use the function without its arguments:

void Print(int const x) { cout << x << endl; }

int main() {
    BinarySearchTree<int> obj1, obj2, obj3;
    obj1.Insert(10);
    obj1.VisitInOrder(Print);
    return 0;
}

full code here: http://pastebin.com/TJmAgwdu

Andy Prowl · Accepted Answer · 2013-06-03 22:04:25Z

3

Your function Insert is a member function, which means it accepts an implicit this pointer. You have to use std::bind() if you want to get a unary functor out of Insert():

if (this != &tree) {
    tree.VisitInOrder(
        std::bind(&BinarySearchTree::Insert, this, std::placeholders::_1));
}

Here is a live example showing the program compiling when the following assignment is present:

obj3 = obj1;

answered Jun 3, 2013 at 22:04

Andy Prowl

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