Still fairly new with C++ and trying to kick it up a notch here. I would like to build a Heap class, with a nested Node class, and add a heap sort aspect to the Heap class. I have done something similar with Java, but I am getting stuck trying to define the nested class in the .cpp file.
#pragma once
#ifndef HEAP_H
#define HEAP_H
template <class T>
class Heap
{
public:
class Node
{
public:
Node(T);
T data;
private:
Node *parent;
Node *left_child;
Node *right_child;
boolean is_root;
};
Heap(T*, int);
sort_it();
private:
T *unsorted_list
Node root;
void build_heap();
void add_node(Node);
void swap_root();
void trickle_down();
void heap_sort();
};
#endif
Now when I go to define my nested class in the .cpp file I cannot simply...
#include "stdafx.h"
#include "Heap.h"
#include <iostream>
//Defining Heap Constructor
Heap::Heap(T* incoming_array, int _size)
{
unsorted_list = incoming_array;
size = _size;
}
//Defining Node Constructor
Heap::Node(T _data)
{
data = _data;
left_child = right_child = parent = Null;
is_root = false;
}
I am not sure if my problem is how I am incorporating the template, or if my syntax for defining the inner class is wrong. Both Generic Programming and Nested Classes are unfamiliar to me in C++
If you use any generic type in nested class you have to specify the template.
template<class T>
class Node
To define the template class constructor outside the class,
template<typename T>
Node<T>::Node(T _data)
Declare the member as follows,
Node<T> root
Related
The question is that in case of stencil out a class via templates, then include it to use as usual: It'll be gotten the error explained in below:
If it is demanded to use struct Something straightforwardly within Node.inl. It needs to include "Node.h" header as follows, but this will comes with some troubles. We violate the rule of one definition, but the template class needs to include their definitions in the same file as they are declared. Otherwise, the compiler will forget to stencil out the member functions upon the instance created. As a result, we can not use these functions via the instance initialized. So how do we manage that while we want to preserve the separateness of declarations and definitions, persist not violate one definition rule?
Node.inl:
#include "Node.h"
void foo(){
struct Something s{1, 2};
}
template <class T>
Node<T>::Node(int data, Node<T> *next) : m_data{data}, m_next{next} {}
template <class T>
void Node<T>::setData(int data) {
m_data = data;
}
template <class T>
int Node<T>::getData() const {
return m_data;
}
template <class T>
void Node<T>::setNext(Node<T> *next) {
m_next = next;
}
template <class T>
Node<T> * Node<T>::getNext() const {
return m_next;
}
template <class T>
void Node<T>::allocMemoryNext() {
m_next = new Node<T>();
}
Node.h:
#ifndef THE1_NODE_H
#define THE1_NODE_H
struct Something{
int x;
int y;
};
template <class T>
class Node {
private:
T m_data;
Node *m_next;
public:
explicit Node(int data = 0, Node *next = nullptr);
void setData(int data);
[[nodiscard]] int getData() const;
void setNext(Node *next);
[[nodiscard]] Node *getNext() const;
void allocMemoryNext();
};
#include "Node.inl"
#endif //THE1_NODE_H
we want to preserve the separateness of declarations and definitions
There is no such "separateness" as far as templates are concerned. In order for anyone to use them, they must be defined. And Node.h provides those definitions.
Node.inl is part of Node.h. You have logically separated the text into different files, but they aren't separate as far as any practical reality is concerned. Every user of Node.h should be getting Node.inl's stuff too, which is why you #include "Node.inl" at the end of the file. Nobody but Node.h should be including Node.inl, so there is no reason for Node.inl to #include "Node.h".
So there is no problem, once you remove the needless include of a thing that is definitely already there.
So i am trying to create a stack class that inherits member functions from a linked list class. The linked list class has no actual implementation of its own; it's essentially an abstract virtual class. Both are template classes. When I try to access a member function using my derived stack class, I am receiving a "no member function declared in class 'Stack'" error. Below is my code. I'm not sure what the issue is. I have included the names of the .h files as well as the : public List sequence in the declaration of the stack class. Please help! If any more code is required for you to answer this question please let me know!! Thank you!
Code for declaration of List parent class
#ifndef LIST221_H
#define LIST221_H
#include "Node221.h"
template <typename T>
class List221 {
public:
List221();
~List221();
virtual int size() const;
virtual bool empty() const;
virtual bool push(T obj); //will push in a new node
virtual bool pop(); //will pop off the top node
virtual bool clear();
protected:
private:
Node<T>* front;
Node<T>* rear;
};
#endif
Code for declaration of Stack class.
Includes List.h file
#include "List221.h"
#include "Node221.h"
template <typename T>
class Stack221 : public List221 <T> {
public:
Stack221();
~Stack221();
T top();
private:
Node<T>* topnode;
};
Example of Member function from List class that I am trying to access.
Also includes List.h at top of page
template <typename T>
bool Stack221<T>::push(T obj) {
Node<T>* o = new Node(obj);
if (topnode == nullptr) {
topnode = o;
}
else {
o->next = topnode;
topnode = o;
}
return true;
}
Error being displayed
error: no ‘bool Stack221<T>::push(T)’ member function declared
in class ‘Stack221<T>’
bool Stack221<T>::push(T obj) {
^
It seems that you have provided an implementation of Stack221<T>::push, but you have not declared that method in your class declaration.
I have a queue.h file like the following.
Is it possible that I can access the head pointer of the queue from Main?
If yes, what should I do in main?
Since the head pointer is a class pointer, and its type is a protected nested class, I don't think I can access it from main.
Therefore, I try to create a function getHead() as public member. However, another problem comes, it is I am using template class. Please guide me how to solve this problem.
my header file:
#include <iostream>
#include <iomanip>
using namespace std;
class PCB
{
public:
int PID;
string fileName;
};
template<class T>
class myQueue
{
protected:
class Node
{
public:
T info;
Node *next;
Node *prev;
};
Node *head;
Node *tail;
int count;
public:
void getHead(Node **tempHead);
};
template<class T>
void myQueue<T>::getHead(Node **tempHead)
{
*tempHead = head;
}
#endif
my main is:
#include "myQueue.h"
#include <iostream>
int main()
{
myQueue<PCB> queue;
//How can I access the Head pointer of my Queue here?
//queue.getHead(&tempHead);
return 0;
}
To acess myQueue::Node from outside the class you need to rewrite your getter function a bit:
template<class T>
myQueue<T>::Node* myQueue<T>::getHead()
{
return head;
}
Then you can use it in main() like this
auto head = queue.getHead();
Note that the usage of auto is important in this case. You still cannot declare any variable of type myQueue<T>::Node or myQueue<T>::Node** outside of myQueue<T>, but you can use auto variables to hold these types.
I am trying to create a binary search tree of Player objects. I have previously defined the Player class. However, when I go to include the player object in the structure for each node of the BST, I get an error that Player is undefined even though I thought I had set up the includes properly.Is there any way for me to go about this without having to rethink my implementation?
I simplified the code a little to demonstrate:
BST header:
class Player;
class BinarySearchTree{
private:
struct Node {
Player info;
Node* left;
Node* right;
};
Node *root;
void Insert(Node*& tree, Player p);
void PrintTree(Node* tree, std::ostream& out);
};
BST.cpp
#include "Player.h"
#include "BinarySearchTree.h"
//all methods implemented afterwards
Player.h
class Player{
private:
std::string* name = new std::string;
int* score = new int;
public:
//....
};
Player.cpp
#include "Player.h"
//...
Compiler needs to see the definition of class Player in header file (BST.h) which you have provided in BST.cpp ( by including "Player.h").
So, BST header should be:-
#include "Player.h" <<<include this file
class Player; <<<remove this forward declaration
class BinarySearchTree
{
private:
struct Node {
Player info;
Here is my problem.
I have a Linked List class as follows:
#include <iostream>
#include "List.h"
template <class Elem>
class LList : public List<Elem> { //List is a virtual base class
protected:
Node <Elem> *head;
Node <Elem> *fence;
Node <Elem> *tail;
int leftCount;
int rightCount;
void init();
void removeAll();
public:
LList();
~LList();
//Rest of methods overridden from List class
//////
};
Then I have a class called SortedLList which inherits from LList as follows:
#include "LinkedList.h"
#include "Helper.h"
template <class Elem>
class SortedLList : public LList<Elem> {
protected:
Helper *helper;
public:
SortedLList();
~SortedLList();
bool insert(const Elem&); //Override insertion method from LList class
};
In the implementation of SortedLList (SortledLList.cpp):
#include "SortedLList.h"
template <class Elem>
SortedLList<Elem>::~SortedLList() {
removeAll();
}
template <class Elem>
bool SortedLList<Elem>::insert(const Elem &_e) {
fence = head;
//Rest of Code..
}
I am having a compiler error that says : Use of undeclared identifier removeAll(). Same thing for fence and head pointers are not being recognized. What did I do wrong?
Thank You.
Because your class is a template there are certain issues that can happen to confuse the compiler. You may think your code is straight forward and easy to understand, and in this case it is. Older compilers used to do their best to guess and compile this code.
However, newer compilers are more strict and fail on all versions of this type of code, in order to prevent programmers from relying on it.
What you need to do is use the this pointer when calling base class functions. That makes the call unambiguous and clear. That would look like this->removeAll().
Another option would be to use a full name qualification like LList<Elem>::removeAll(). I prefer using this because it is easier to read.