Thread: Trying to get a subclass example to work...

I'm using code::blocks.
the code below notes:
Fract.cpp must be compiled and linked into
the project, or else Fraction frunction defs must be
copied into this file.

Does anyone know how to do the former? I tried adding the Fract.cpp with the main.cpp. I get a compiler error that "Fract.h file or directory does not exist."

Code:

// Exercise 17.01.02
// Adds set_float() funct. and tests it.
//
#include <iostream>

#include "Fract.h" // Declaration of Fraction class must
                   // be placed in Fract.h.
using namespace std;

// Note: Fract.cpp must be compiled and linked into
// the project, or else Fraction frunction defs must be 
// copied into this file.

class FloatFraction : public Fraction {
public:
    FloatFraction() {} // Default constr:
                       // F.F. inherits no contr’s!

    FloatFraction(double x) {set_float(x);}    // NEW CONSTR.

    double get_float() {
       double x = get_num();
       return x / get_den();
    }
    
    void set_float(double x) {             
         int n = static_cast<int>(x * 100.0);
         set( n, 100 ); 
    } 
};

int main() {
    FloatFraction fract1(0.75), fract2(1.5), fract3(0.333);

    cout << "Value of fract(0.75) is " << fract1 << endl;
    cout << "and its get_float val is: " << fract1.get_float();
    cout << endl;
 
    cout << "Value of fract(1.5) is " << fract2 << endl;
 
    cout << "Value of fract(.333) is " << fract3 << endl;

    system("PAUSE");
    return 0;
}

Originally Posted by manasij7479

Then it simply doesn't.
1.File Class.h =>Contains you base class declaration. This should be included in main.cpp and Class.cpp both, and suitable guarded.
2.File Class.cpp => Should contain the definitions of the functions of the base class. Compile this with the main program or add it to the project to be done automatically.
3.main.cpp => Home of int main() and anything else you might want to add.

1. This is where I'm confused. You're right there is no file Fract.h. Is this something we have to create? Is this something "code wise" we have to add to main.cpp and fract.cpp?

2.They do and I did locate Fract.cpp in the directory where main.cpp resides and then added it to my project.

Head hurts

You're right there is no file Fract.h. Is this something we have to create?

Now, I'm confused..How do you expect to use Fract.h if it is not there?

I'll guess that this is about a lesson in inheritance.
So, here it goes:
You've to create Fract.h with the declaration of the fraction class, and put the corresponding definitions in the .cpp file.

The main looks ok.

Originally Posted by grumpy

Inheritance has nothing to do with header files, actually.

It is only by convention that programmers often create a header file and a source file corresponding to a particular class. This is done for the convenience of programmers. The compiler does not care, one way or the other. The only thing needed is that each class, each of its member functions, and each of its static members are defined exactly once across all the source files in a project.

However, if you are going to tell the preprocessor to #include "Fract.h", then Fract.h must exist.

I know inheritance has nothing to do with header files, but in the example he posted, the base class was in a separate file, as you said..for convenience.