Returning an object from dequeue function? - c++

Question

I am trying to get a linked-list class-based queue that holds objects of type "Student", but I've been trying for two days to get this thing to work. Now I am seeing errors of exceptions at the copy constructor of the "Student" class and the return of the dequeue function, and am at a complete loss since I don't even know what that means.
My main issue, from what I can tell, is when I try to assign the return of the dequeue to an object, there is an issue with the fact that I'm using the standard = operator and not a custom operator= for the class. Then again, I am relatively new to classes so I don't know if this is actually the issue.
This is the main code that uses all my files:
#include <iostream>
#include <fstream>
#include <string>
#include "Student.h"
#include "Queue.h"
int main(void)
{
char TempFName[15], TempSName[20];
long Tid_num;
int Tage;
float Tgpa;
Student Student1, StudentA;
queue q1;
int no, temp;
ifstream ip("input.txt");
// modify for your location
ip >> no; /* read in the number of Students */
for (temp = 0; temp < no; temp++)
{
/* read in the Student data in file format */
ip >> TempFName;
Student1.assignFName(TempFName);
ip >> TempSName;
Student1.assignSName(TempSName);
ip >> Tid_num;
Student1.assignId(Tid_num);
ip >> Tage;
Student1.assignAge(Tage);
ip >> Tgpa;
Student1.assignGpa(Tgpa);
q1.enqueue(Student1);
}
ip.close();
queue q2(q1);
q2.enqueue(StudentA);
q1.enqueue(StudentA);
cout << "details for queue 2 are as follows" << endl;
for (temp = 0; temp < no + 1; temp++)
{
Student1 = q2.dequeue();
Student1.print();
}
cout << "There are " << Student1.getNum() << " Student objects in existence";
return 0;
}
My files are:
Student.cpp:
#include <iostream> // need for cout, etc
#include "Student.h"
using namespace std;
Student::Student(const Student& s)
{
firstname = s.firstname;
surname = s.surname;
id_num = s.id_num;
age = s.age;
gpa = s.gpa;
count++;
}
Student::~Student() { count--; }
void Student::assignFName(string tempFName)
{
firstname = tempFName;
}
void Student::assignSName(string tempSName) { surname = tempSName; }
void Student::assignId(long Tid_num) { id_num = Tid_num; }
void Student::assignAge(int Tage) { age = Tage; }
void Student::assignGpa(float Tgpa) { gpa = Tgpa; }
string Student::getSName() { return surname; }
long Student::getId_num() { return id_num; }
int Student::getAge() { return age; }
float Student::getGpa() { return gpa; }
int Student::getNum() { return count; }
void Student::print() const
{
cout << firstname << " " << surname << " " << id_num << " " << age << " ";
cout << gpa << endl; // could do on same line, but do on next line just so can see that can be multiple lines, etc
}
int Student::count = 0;
Student.h:
#pragma once
//Module.h
#ifndef STD_H
#define STD_H
#include <string>
using namespace std;
class Student
{
public:
// just include one constructor definition here to show how it is written if do inline
Student(string fn = "nofirstname", string sn = "nosurname", long i = 0000, int a = 0, float s = 0)
:firstname(fn), surname(sn), id_num(i), age(a), gpa(s) {
count++;
}
Student(const Student& s);
~Student();
void assignFName(string tempFName);
void assignSName(string tempSName);
void assignId(long Tid_num);
void assignAge(int Tage);
void assignGpa(float Tgpa);
string getFName() { return firstname; } // just include one method here to show how it is written if do inline
string getSName();
long getId_num();
int getAge();
float getGpa();
void print() const;
static int getNum();
private:
string firstname, surname;
long id_num;
int age;
float gpa;
static int count;
};
#endif
queue.cpp:
#include "Queue.h"
#include "Student.h"
#include <iostream>
#include <stdlib.h>
void queue::enqueue(Student value) {
QueueNode* temp = new QueueNode(value); //allocating memory for the newly created node, with a value passed into it
if (tail == NULL) { //If there is no tail (i.e. only 1 block in the queue)...
head = tail = temp; //The tail and head are now the one block
return; //
} //
tail->next = temp; //The next address of the tail is made to equal the temporary node
tail = temp; //The tail becomes the temporary node
delete temp;
}
Student queue::dequeue() {
Student a;
if (head == tail) {//if only one node is there
head = tail = NULL;
} else {
head = head->next;
}
if (head == NULL) {
exit(1);
}
a = head->value;
return a;
//Student a;
//QueueNode* temp = head; //store the current head node of the queue
//delete (temp);
//if (head != NULL) {
// head = head->next;
//
//} else {
// tail = NULL;
// //return a;
//}
//a = head->value;
//return a;
}
void queue::printQueue() {
int count = 1; //initiazling counter variable as 1 so that the counter does not start at 0
while (head != NULL) //while the are still blocks in the queue
{
//cout << "\n\tBlock number " << count << " pushed: " << ; //print the block that was just inserted and what position it is at
head->value.print();
head = head->next; //equate the node to the next address
count++; //increment the counter
}
}
queue::~queue() {
head = tail = NULL;
}
queue::queue(const queue& q) {
QueueNode* hold = q.head;
QueueNode* temp, * oldtemp;
if (hold == q.tail)
{
temp = new QueueNode;
head = temp;
tail = temp;
}
else
{
temp = new QueueNode;
head = temp;
while (hold != q.tail)
{
// get the value at the node looking at on queue 'r' list
temp->value = hold->value;
// move to the next entry on 'r' list
hold = hold->next;
oldtemp = temp;
temp = new QueueNode;
oldtemp->next = temp;
}
tail = temp;
}
}
queue::queue() {
head = tail = NULL;
}
//queue::sizeOfQueue() { //function to return the number of nodes in the queue
// //takes in the pointer to the queue so that the function knows which queu to get the size of
// int size = 0; //intialize size integer to be returned
// while (node != NULL) { //for as long as a NULL node is not reached
// node = node->next; //equate the node to the next address
// size++; //increment the size integer
// } //eventually the node will reach the end of the queue where the next address is NULL (because there are no other nodes)
// return size; //return the integer for the size
//}
queue.h:
#pragma once
#include "Student.h"
#include "Node.h"
class queue {
public:
queue();
queue(const queue& q);
~queue();
void enqueue(Student value);
Student dequeue();
void printQueue();
private:
QueueNode* head;
QueueNode* tail;
};
Node.cpp:
#include "Queue.h"
#include "Node.h"
#include "Student.h"
#include <iostream>
QueueNode::QueueNode() {
value = Student();
next = NULL;
}
QueueNode::QueueNode(Student val) {
value = val;
next = NULL;
}
QueueNode::~QueueNode() {
value.~Student();
next = NULL;
}
Node.h:
#pragma once
#include "Student.h"
class QueueNode {
friend void enqueue(Student value);
friend void dequeue();
friend void printQueue();
public:
QueueNode* next; //PUBLIC VARIABLE
Student value;
QueueNode();
QueueNode(Student val);
~QueueNode();
private:
};
The input file that gets the details for the "Student" objects that go in the queue:
3
joe bloggs 40001 24 2.1
mary doe 40002 19 3.9
john boyd 40003 18 1