Why does this not work ?

[magic wren]

I have a main.cpp file

#define OLC_PGE_APPLICATION
#include "olcPixelGameEngine.h"
#include "supp.cpp"

class renderer: public DrawFunctions
{
public:
    bool OnUserCreate() override
    {
        FillScreen(olc::Pixel(255 , 255 , 255));
        DrawAxes(olc::Pixel(0 , 0 , 0));

        return true;
    }

    bool OnUserUpdate(float fElapsedTime) override
    {
        return true;
    }
};

And another file named supp.cpp

#define OLC_PGE_APPLICATION

#include "olcPixelGameEngine.h"

class DrawFunctions : public olc::PixelGameEngine
{
public:

    void FillScreen(olc::Pixel pixel_type)
    {
        for (int i=0 ; i<ScreenHeight() ; i++)
        {
            for (int j=0 ; j<ScreenWidth() ; j++)
            {
                Draw(j , i , pixel_type);
            }
        }
    }

    void DrawAxes(olc::Pixel pixel_type)
    {
        for (int i = 0 ; i<ScreenHeight() ; i++)
        {
            Draw((int)(ScreenWidth() / 2) , i , pixel_type);
        }

        for (int j = 0 ; j<ScreenWidth() ; j++)
        {
            Draw(j , (int)(ScreenHeight() / 2) , pixel_type);
        }
    }
};

why does this not work ?

[cursive bridge]

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[magic wren]

i get atleast 500 errors, cannot even put them here

but they are all previous definition and redefinition errors.

for eg

      |              ^~~~~~~~~~~~~~~
In file included from main.cpp:2:
olcPixelGameEngine.h:6602:14: note: ‘virtual void olc::PixelGameEngine::olc_ConfigureSystem()’ previously defined here
 6602 |         void PixelGameEngine::olc_ConfigureSystem()

[cunning blaze]

#include "supp.cpp"
Don't include a cpp file?

[magic wren]

yeah i tried to then put that stuff in a header file and compile supp.cpp separately and then link against it

idk what goes in the header file ?

[cunning blaze]

Optimally you should only put function declarations in a header file

With implementations of those functions in a separate cpp