CODEWITHSUNDEEP
c++templatesrecursion
Alex Fish
Alex Fish

Reputation: 778

How should I call function with template recursively?

I'm trying to create a tree class in c++ and i'm not sure how should I use the templates when I am using recursion.

for example I have the following function:

template <typename Data>
void destroyTree(typename AVLTree<Data>::Node* element) {
    if(!element) {
        return;
    }
    destroyTree(element->getLeft());
    destroyTree(element->getRight());
    delete element;
}

or should it be:

template <typename Data>
void destroyTree(typename AVLTree<Data>::Node* element) {
    if(!element) {
        return;
    }
    destroyTree<Data>(element->getLeft());
    destroyTree<Data>(element->getRight());
    delete element;
}

then if I call it suppose from the following function:

template <typename Data>
void AVLTree<Data>::function() {
    destroyTree(root);
}

or:

template <typename Data>
void AVLTree<Data>::function() {
    destroyTree<Data>(root);
}

I've tried to combine most of the possibilities above but I always get an error. usually it's a non matching function for call to

If someone has some experience with that issue please help me.

Thank you.

If I use Nawaz's suggestion I get the following error:

Internal Builder is used for build ** g++ -O0 -g3 -Wall -c -fmessage-length=0 -oAVLTest.o ..\AVLTest.cpp g++ -oAVLTree.exe AVLTest.o AVLTest.o: In function ZN15Data_Structures7AVLTreeIiE4Node7getLeftEv': C:/Users/Alex/workspace/AVLTree/Debug/../AVLTree.h:(.text$_ZN15Data_Structures11destroyTreeIiEEvPNS_7AVLTreeIT_E4NodeE[void Data_Structures::destroyTree(Data_Structures::AVLTree::Node*)]+0x47): undefined reference toData_Structures::AVLTree::Node::~Node()' collect2: ld returned 1 exit status Build error occurred, build is stopped Time consumed: 532 ms.

what can I do with that?

all relevant code is here.

Upvotes: 4

Views: 155

Answers (1)

Sarfaraz Nawaz
Sarfaraz Nawaz

Reputation: 361362

This is correct:

//in the first case
destroyTree<Data>(element->getLeft());
destroyTree<Data>(element->getRight());

//in the second case
destroyTree<Data>(root);

That is, you have to specify the template argument, as it cannot be deduced by the compiler from the function argument because it is a non-deducible context.

Upvotes: 5

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