writing file in header c++ - c++

Question

I have 3 files, book.h, book.cpp, bookdriver.cpp. I want to know if the ISBNs in a list are found in the array using binary search.
book.h:
using namespace std;
ofstream fout("output2.txt");
class Book
{
string author; // A string for the name of the author
string title; //A string for the book title
int ISBN; //A long integer for the ISBN
public:
Book(); //A default constructor
void print();
int getISBN() const; //A const function GetISBN that returns the integer containing the ISBN.
int binary_search(Book, int, int, int);
};
book.cpp- also includes print function which uses fout
#include "book.h"
//iterative binary search function, returns location of ISBN in array if present
int Book::binary_search(Book arr[], int x, int n, int ISBN)
{
while (n >= x)
{
int midpt = x + (n - x) / 2;
//if ISBN is in midpoint
if (arr[midpt].getISBN() == ISBN)
{
return midpt;
}
//if ISBN is greater than midpoint, ignore left side of array
if (arr[midpt].getISBN() < ISBN)
{
x = midpt + 1;
}
//if ISBN is smaller, ignore right side of array
else
{
n = midpt - 1;
}
}
//if ISBN not present
return -1;
}
bookdriver.cpp
#include "book.h"
const int num = 10; //number of book objects the array should hold *can be changed*
int main()
{
Book book_array[num] = {}; //array can hold num book objects
for (int c = 0; c < num; c++)
{
book_array[c] = Book();
book_array[c].getData(data); //reading book information
}
//read file
ifstream fin("bookISBN.txt");
int find_ISBN;
while (fin >> find_ISBN)
{
bool match = false;
int count = 0;
int result = binary_search(book_array[10], 0, num - 1, find_ISBN); //error here
if (result == -1) //if ISBN not found
{
fout << "Sorry, the ISBN " << find_ISBN << " is not found." << endl;
}
else
{
fout << "The ISBN " << find_ISBN << " is found in the system!" << endl;
}
count++;
}
return 0;
}
I'm using fout in both book.cpp and bookdriver.cpp so I have ofstream fout (output2.txt) in the header but I'm getting linker errors(Error LNK2005) in vs.
I think because of the one definition rule, fout is defined twice?

Answer 1

Here's a start:
#include <iostream>
#include <fstream>
using namespace std;
const int num = 2;
class Book
{
public:
Book(){};
string author;
string title;
int ISBN = 0;
int data;
};
int binary_search (Book arr[num], int x, int n, int ISBN, int overflow)
{
int mid = (x + n) / 2;
if (x == mid || n == mid)
overflow++;
if (overflow > 100)
return false;
if (arr[mid].ISBN > ISBN)
return binary_search(arr, x , mid, ISBN, overflow);
else if (arr[mid].ISBN < ISBN)
return binary_search(arr, mid, n , ISBN, overflow);
return true;
}
int main() {
ofstream fout("output2.txt");
ifstream fin("bookISBN.txt");
int find_ISBN;
Book book1;
book1.title = "Alice in Wonderland";
book1.author = "C.S. Lewis";
book1.ISBN = 1;
Book book2;
book2.title = "Wuthering Heights";
book2.author = "Emily Bronte";
book2.ISBN = 2;
Book book3;
book3.title = "Moby Dick";
book3.author = "Herman Melville";
book3.ISBN = 25;
Book book_array[num] = {book1, book2};
while (fin >> find_ISBN)
{
int result = binary_search(book_array, 0, num, find_ISBN, 0);
if (result == false)
{
fout << "Sorry, the ISBN " << find_ISBN << " is not found." << endl;
}
else
{
fout << "The ISBN " << find_ISBN << " is found in the system!" << endl;
}
}
fin.close();
fout.close();
return 1;
}