header and implementation files...

[khris]

Hello everyone, I need a bit of help with this program. It's a simple program I am coding to practice making header and implementation files. The program is not compiling and I have no idea how to make it work at this point. I just want the user to input a number, then I want to convert that string into an integer and output to the screen. Here is what I have so far:

big_nat.h

#include <iostream>

class Big_Nat {
	string str;
	int s_int;
public:
	Big_Nat();
}

big_nat.cpp

#include <iostream>
#include "big_nat.h"

Big_Nat::Big_Nat(str)
{
	s_int = atoi(str.c_str());
}

Big_Nat_test.cpp

#include "big_nat.h"
#include <iostream>

using namespace std;

int main()
{
	string s;

	cout << "Give x : "; getline(cin,s,'\n');
	Big_Nat x(s);
	cout << x << endl;

	return 0;
}

Do I need to include iostream in each of the files? What else am I doing wrong? Any help will be appreciated. Thanks!

[vlad61]

If you are using strings don't you need to declare so with #include <string> ?

[MottMan]

How to create a header:

#ifndef HEADER-NAME-IN-CAPITALS_H
#define HEADER-NAME-IN-CAPITALS_H

//includes
//functions/classes/code

#endif 

How to implement it:

#include "header-name-in-capitals.h"

//includes
//code 

Just add the ifndef, define, and endif, and it should work.

[LB]

Big_Nat() on line7 of big_nat.h takes no parameters, and then in big_nat.cpp it takes a parameter of type "str". You need to change the one in big_nat.h to be Big_Nat(std::string); and the one in big_nat.cpp to be Big_Nat::Big_Nat(std::string str)

@MottMan: Macros do not have to be in all caps, that is simply a common thing to do. It can be any case combination.

[khris]

Thank you all so far. I have taken the advice given in the replies but my program still comes up with many errors. Maybe I am not compiling correctly. I am creating the files in Notepad(simple text editor in Windows) and compiling with g++. In the console window, I type in "g++ big_nat.cpp Big_Nat_test.cpp -o big_nat". Is there another way I need to compile this so that the files link together? Also, I am getting errors such as "'cout' was not declared in this scope." Why is this? I have declared that I am using the std namespace... Here is what I have so far:


big_nat.h

#ifndef big_nat_h
#define big_nat_h
#include <iostream>
#include <string>

class Big_Nat {
	string str;
	int s_int;
public:
	Big_Nat(std::string);
}
#endif 

big_nat.cpp

#include <iostream>
#include "big_nat.h"
#include <string>

Big_Nat::Big_Nat(std::string str)
{
	s_int = atoi(str.c_str());
}

Big_Nat_test

#include "big_nat.h"
#include <iostream>
#include <string>

using namespace std;

int main()
{
	string s;

	cout << "Give x : "; getline(cin,s,'\n');
	Big_Nat x(s);
	cout << x << endl;

	return 0;
}

[khris]

Alright, I changed some stuff around and got less errors but I am still getting the error "no match for 'operator<<' in 'std::cout << x'". Here is what I have now:
big_nat.h

#ifndef big_nat_h
#define big_nat_h
#include <iostream>
#include <string>

class Big_Nat {
	std::string str;
	int s_int;
public:
	Big_Nat(std::string);
};
#endif 

big_nat.cpp

#include <iostream>
#include "big_nat.h"
#include <string>

Big_Nat::Big_Nat(std::string str)
{
	s_int = atoi(str.c_str());
};

Big_Nat_test.cpp

#include "big_nat.h"
#include <iostream>
#include <string>

using namespace std;

int main()
{
	std::string s;

	std::cout << "Give x : "; getline(std::cin,s,'\n');
	Big_Nat x(s);
	std::cout << x << std::endl;

	return 0;
}

I am confused about using namespace std. I thought if I declared that, then I could use cout instead of std::cout, but it seems that if I don't use std::cout, I get many errors. Can anyone tell me what I am doing wrong here?

[LB]

cout doesn't know how you want it to print out x, because x is your own class and it doesn't define any operators to be nice to cout.

[khris]

thank you L B...I have figured it out with your hint. Here is what I have:

big_nat.h

#ifndef big_nat_h
#define big_nat_h
#include <iostream>
#include <string>

class Big_Nat {
	std::string s;
	int s_int;
public:
	Big_Nat(std::string);
	int to_int();
};
#endif 

big_nat.cpp

#include <iostream>
#include "big_nat.h"
#include <string>

Big_Nat::Big_Nat(std::string s)
{
	s_int = atoi(s.c_str());
};
int Big_Nat::to_int()
{
	return s_int;	
};

Big_Nat_test.cpp

#include "big_nat.h"
#include <iostream>
#include <string>

using namespace std;

int main()
{
	std::string s;

	std::cout << "Give x : "; getline(std::cin,s,'\n');
	Big_Nat x(s);
	std::cout << x.to_int() << std::endl;

	return 0;
}

[LB]

One last thing, you never use line 7 in big_nat.h

[khris]

Line 5 of big_nat.cpp. Isn't the std::string s the one I declared in line 7 of big_nat.h? I'm a bit confused now..

[gcampton]

No when you declare parameters in functions they are copies (assuming your not using references or pointers). you don't need to declare them a second time:

#include <iostream>
#include <string>
using namespace std;

void printFunction(string s) // string s does not need to be initiated anywhere. 
{ //we have done so here.

    cout << s; // string 'abcd' is sent to the function and 's' becomes a copy of 'abcd', 
    //meaning it contains the same data "Hello World"
}

int main()
{
    string abcd = "Hello World"; // we create a string called 'abcd'
    printFunction(abcd);  // we send 'abcd' to the function
    return 0;
}

[khris]

Ah, I understand now. How about variables used in a function? Do I declare them in the private section in the header file or declare them in the implementation file?

[gcampton]

It depends, if you need something to have global scope then in the header file is probably the best place for it, but if it's just a quick variable your only going to use in the one function then declaring in the function is fine.

#include "header.h"
#include <iostream>
#include <string>
using namespace std;

void h::function()
{
   int i = 10;  // i only a local var we use in this function only;
   cout << "Countdown in:" << endl;
   while ( i > 0 )
   {
      cout << i << endl;
      i--;
   }
   fileName = "HotTomatos.txt";  // this is global, (private string in header) because we are going to use it in multiple places.
   cout << "The filename we use throughout the whole program is called: " << fileName;
}

int main()
{
   h h;

   h.function();

   return 0;
}
      

#ifndef HEADER_H
#define HEADER_H

class h
{
   public:
      void function();

   private:
      string fileName;
};

#endif 

[khris]

Thanks gcampton, I'm glad I learned this sooner than later..I was wondering why I was getting errors saying that some of my variables weren't declared even though I thought they were...