virtual bool error C4430

[TimHallyburton]

Hello there!

Thanks for visiting my topic, to get it straigt, I am seeking for help. Before you ask me: Nope, im not coding since yesterday, yes i googled my problem, yes i asked my mentor for help (he had no clue either) so don't think i want to waste your time or abuse this forum :)

First off I'll show you the problem:

#pragma once
#ifndef VERGLEICHER_H
#define VERGLEICHER_H
#include "punkt.h"

using namespace std;

class Vergleicher{
public:
	virtual bool kleiner(const Punkt& p1, const Punkt& p2) = 0;
};

#endif /* VERGLEICHER_H */

this class was intented to inherit the function kleiner ( this means smaller) to 3 other classes but unfortunatley I get this error:

"error C4430: missing type specifier - int assumed. Note: C++ does not support default-int"

Here are some things I already tried to fix this problem:

-remove #pragma from code
-remove function arguments (this was a bad idea)
-remove all commands to the compiler
-write the class in the same .h than the other 3 classes
-delete and rewrite the class
-adding/removing namespace std (no effect at all)
-switching (const Punkt& p1 ....) to (Punkt p1, ...)
-trying to use a virtual int instead of a virtual bool (got same error)
-trying to use no virtual class at all (still same error?!?!?!?!)
-writing the code on a friends laptop with another version of Visual Studio
-google it
-google it again
-annoy my friends to help me
-annoy my mentor to help me
-google it again


########################################################
############ SOLUTION ##################################
########################################################

#pragma once
#ifndef VERGLEICHER_H
#define VERGLEICHER_H

struct Punkt {                                                     //I declared this struct here instead 
    int x, y;                                                           //of using compiler orders
};

class Vergleicher{
public:
	virtual bool kleiner(Punkt& p1,Punkt& p2) = 0;   // <- they are not const any longer!
};

#endif /* VERGLEICHER_H */ 

Now if u think its a problem that point p1 and p2 are not const anylonger, dont be worried! When inheriting the abstract class (Yep thats the WHOLE class) u can add "const" again and he wont overwrite/reinterpret the method!

Thanks for everyone who helped me to figure this finally out:

Branflakes91093
TheIdeasMan
Disch

Have a great weekend gentlemen :)

[Branflakes91093]

The compiler doesn't know what Punkt is.

[TheIdeasMan]

Do you need to include the header file that declares the class Punkt?

The type Punkt is not defined in your code, you must define types for parameters in a function declaration.

Also try to avoid using namespace std; - it brings in lots of stuff into the global namespace, and can cause conflicts in names of variables & functions.

Either put std:: before each std thing. I do this for things which are frequently used in a file - for example if I use std::find once or twice.

Or you can have a using std::cout; statement say, for things which are used a lot.

HTH

[TimHallyburton]

I'm sorry, I accidentally posted the wrong version of the code :(
thanks for the quick answer tho!
I updated my post now ;)

[TheIdeasMan]

And you still have problems? Can you post the actual error in full?

[Disch]

It might be a circular dependency.

Does punkt.h include vergleiche.h? If yes, you have a problem.

To solve, do not include punkt.h from the header file. Instead, just forward declare the class:

#pragma once
#ifndef VERGLEICHER_H
#define VERGLEICHER_H


//#include "punkt.h"  <-  bad.  Move this to the cpp file, not the h file
class Punkt;  // <- good

using namespace std;



class Vergleicher{
public:
	virtual bool kleiner(const Punkt& p1, const Punkt& p2) = 0;
};

#endif /* VERGLEICHER_H */ 

[TimHallyburton]

Sadly I have :(
The Compiler says:



Fehler 1 error C4430: Fehlender Typspezifizierer - int wird angenommen. Hinweis: "default-int" wird von C++ nicht unterstützt. c:\users\tim\downloads\vergleicher.h 10 1 Praktikum13-1-20



(translated:

Error 1 error C4430: missing typespecifier - int assumed. Note: C++ does not support default-int". (....)
)
if it helps I can also post other classes and stuff, but I dont think it will help a lot, the std::stuff is a good idea for the rest of the code, but here I didnt want to have any output at all so i dont know if it helps.
Thanks a lot tho :)

[TimHallyburton]

Hello Disch,
thanks for the quick answer, I tried to declare the struct Punkt (For some reason it HAS to be a struct, this was one of the tasks [which is totally pointless I think]) like u said, I still get the same error and my compiler doesn't seem to find any other problems :/

[TheIdeasMan]

Yeah the std:: stuff doesn't have anything to do with your problem, I just try to break people out of their bad habits early (not that it is your fault - there is lots of code on the net has using namespace std;, even Bjarne Stoustrup does it :D)

I don't have any other suggestions, so will have to leave you in the very good hands of Disch, who has vastly more experience than me.

[Disch]

Can you show me 2 more things?:

1) punkt.h

2) copy/paste of the #include lines in whatever cpp file is causing this error (not the header).

[TimHallyburton]

GOOD NEWS ********************

it works! I did what Disch told me (declare: struct Punkt;) on top of the abstract class
and then just removed "const" from the argument list!
I don't really know why this works, but I am currently the happiest man on earth!!! :)

I will edit my post now and add a solution, so everybody can see it on the first post, thank you guys so much!!!