CODEWITHSUNDEEP
c++
boogiewoogie
boogiewoogie

Reputation: 3

Struct Node in tree class is not being recognized when I compile

I get this error from the compiler (I get like 5 of these errors):

./Tree.h:14:2: error: unknown type name 'Node'
         Node *getParent(Node *child);

Here is my Tree.h class:

#ifndef TREE_H_    
#define TREE_H_

class Tree {
public:
    Tree(int arr []);
    Node *getParent(Node *child);
    Node *getRightChild(Node *parent);
    Node *getLeftChild(Node *parent);
private:
    struct Node {
        Node *parent;
        Node *left;
        Node *right;
        int value;
    };
    Node *root;
    int size;
};

#endif

Upvotes: 0

Views: 137

Answers (2)

catnip
catnip

Reputation: 25388

Another way to get this code to compile is to forward declare Node:

class Tree {
private:                      // add this
    struct Node;              // and this
public:
    Tree(int arr []);
    Node *getParent(Node *child);
    Node *getRightChild(Node *parent);
    Node *getLeftChild(Node *parent);
private:
    struct Node {
        Node *parent;
        Node *left;
        Node *right;
        int value;
    };
    Node *root;
    int size;
};

This works because you are only using pointers-to-Node (Node *) in your outer class. If you wanted to use a bare Node then you would have to use the other solution here.

Upvotes: 0

Hassan Ashas
Hassan Ashas

Reputation: 580

Change the arrangement of code to this and it should work fine:

#ifndef TREE_H_
#define TREE_H_

class Tree {
private:
    struct Node {
        Node *parent;
        Node *left;
        Node *right;
        int value;
    };

    Node *root;
    int size;

public:
    Tree(int arr []);
    Node *getParent(Node *child);
    Node *getRightChild(Node *parent);
    Node *getLeftChild(Node *parent);
};

The compiler reads the code in sequence. In your case, you have defined your Node struct after defining your functions (which are using instances of your Node struct) and hence, it is unable to recognize the Node type.

Declaring your Node struct before declaring your functions will make your code work.

Upvotes: 1

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