‘sortBook’ was not declared in this scope [duplicate] - c++

Question

This question already has answers here:
Sorting a vector of custom objects
(14 answers)
Closed 1 year ago.
I cannot solve the error - main.cpp:31:34: error: ‘sortBook’ was not declared in this scope in the line sortBook(arr,arr+n,comparator);
I apologize for asking a question that should have a simple solution, but it's driving me nuts. I've checked for all the common errors.
#include<iostream>
using namespace std;
class BOOK{
private:
char bookname[20];
float bookprice;
public:
void getBookDetails()
{
cout<<"Enter the Book Name:";
cin>>bookname;
cout<<"Enter the Book Price:";
cin>>bookprice;
}
void displayDetails()
{
cout<<"Book Name:"<<bookname<<endl;
cout<<"Book Price:"<<bookprice<<endl;
}
};
bool comparator(string a,string b)
{
return a<b;
}
int main()
{
int n=5;
string arr[]={"sandwich","apple","banana","zombie","pear"};
sortBook(arr,arr+n,comparator);
for(int i=0;i<n;i++)
{
cout<<arr[i]<<" ";
}
}

Answer 1

I think it's just that you have not declared sortBook function anywhere and trying to use it.

Answer 2

Your error shows up because you have not defined the method "sortBook".
There are 2 ways to fix this error:
Define your own "sortBook" method in your class.
Use C++ sort method that is defined in "Algorithm". Below is my code that uses this sort method. You have to "include algorithm " at the top of your file, and call the sort method.
#include<iostream>
#include<algorithm> ////// YOU SHOULD INCLUDE THIS STATEMENT
using namespace std;
class BOOK{
private:
char bookname[20];
float bookprice;
public:
void getBookDetails()
{
cout<<"Enter the Book Name:";
cin>>bookname;
cout<<"Enter the Book Price:";
cin>>bookprice;
}
void displayDetails()
{
cout<<"Book Name:"<<bookname<<endl;
cout<<"Book Price:"<<bookprice<<endl;
}
};
bool comparator(string a,string b)
{
return a<b;
}
int main()
{
int n=5;
string arr[]={"sandwich","apple","banana","zombie","pear"};
std::sort(arr,arr+n,comparator); // HERE, YOU CALL : sort()
for(int i=0;i<n;i++)
{
cout<<arr[i]<<" ";
}
}
Note: My code above compiles with no errors. It runs and produces the correct output. Please let me know if you have any other issues.