Template Based Error:

As a part of creating an AVL tree, i ran into the following error when debugging:"error: no matching function for call to ‘getline(std::basic_string&, std::string&)". i am somewhat sure that this error is somehow related to template because without using generic code it works. could not figure out what am doing wrong. Error pops up in AVLTree* BuildAVLTree(T filename);

any help is appreciated.

#include<iostream>
#include <cstdlib>
#include <bits/stdc++.h>
#include <array>
#include <string>
#include <fstream>
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using std::string;



/* Create an AVL tree as subclass BST */
template <class T>
class AVLTree{
public:

    AVLTree() // constructor
    {
        int    key;
        AVLTree *left;
        AVLTree *right;
    }
// create a new node
    AVLTree<AVLTree>* addNode(int data)
    {
        AVLTree<AVLTree>* node = new AVLTree;
        node->key = data;
        node->left = node->right = NULL;
        return (node);
    }
//destructor

 ~AVLTree()
    {
        delete left;
        delete right;
        cout << "\nDeleting " << this->key << endl;
    }

// Function visit inorder traversal on tree
    void printBT(AVLTree<AVLTree>* root)
    {
        if (root == NULL) {
            return;
        }

        printBT(root->left);
        cout << root->key << " ";
        printBT(root->right);
    }

// Function: add a key into a BST (overloaded)
    AVLTree<AVLTree>* addNode(AVLTree* root, T key)
    {
        // if the root is null, create a new node and return it
        if (root == NULL) {
            return addNode(key);
        }
        // if key < root node, recurse left subtree
        if (key < root->key) {
            root->left = addNode(root->left, key);
        }
            // if key > node, recurse right subtree
        else {
            root->right = addNode(root->right, key);
        }
        return root;
    }

// Function: Construct balanced BST from given sorted array.
    void convert(T keys[], T low, T high, AVLTree* &root)
    {
        // base case
        if (low > high) {
            return;
        }
        // find the middle element of the current range
        int mid = (low + high) / 2;

        // construct a new node from the middle element and assign it to the root
        root = addNode(keys[mid]);

        // left subtree of the root will be formed by keys less than middle element
        convert(keys, low, mid - 1, root->left);

        // right subtree of the root will be formed by keys more than the middle element
        convert(keys, mid + 1, high, root->right);
    }

// Function: Construct balanced BST from the given unsorted array


   // AVLTree* BuildAVLTree(T arr[])
   AVLTree* BuildAVLTree(T filename)
    {
        ifstream outputFile (filename);
        if (outputFile.is_open()) {
            string line;
            getline (filename,line);
               cout << line << '\n';

           outputFile.close();
        }

        else cout << "Unable to open file";

        /* 
        intention is to read filenmame from a text file then create an array
        based on the reading. BUT still need the above code to work first
        
        */

        const int arrSize = 8;
        int arr[] = {1,2,3,4,5,6,7}; // anything just to make things work for now
        // sort the keys first
        std::sort(arr, arr + arrSize);

        // construct a balanced BST
        AVLTree* root = NULL;
       convert(arr, 0, arrSize - 1, root);
        // return root node of the tree
        return root;
    }
    
};

int main() {

    string filename ="inputFile_A3"; // input file name
    AVLTree<string>* avl;
    avl = avl->BuildAVLTree(filename); // this line is the source of the error

}

Last edited on

lastchance (6980)

getline (filename,line);
Did you mean
getline (outputFile,line);

or, better still, with some renaming of variables in the code around it:
getline (inputFile,line);

seeplus (6597)

Shouldn't T be the type of the key? ie L22 should be T key; ?? Same with L27 etc etc

L97. filename should always be of type std::string (or better const std::string&) - so you don't need to use T here (L96 was right!)

Also note the destructor is not correct - as it doesn't traverse the tree deleting every node.

coder777 (8444)

error: no matching function for call to ‘getline(std::basic_string&, std::string&)

Line 102: You need to provide outputFile not filename

jaymann (4)

Thank you so much. i corrected my code as suggested and it work! also i adjusted other lines as required.
Best,

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