Unable to inherit protected variables

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Hi,
I am trying to implement a sorting method in a list in which I have used some protected variables count, entry[maxlist] etc.
List.h

template < class List_entry >
class List
    {
    public:
    //etc etc
    protected:
    int count;
    int entry[maxlist];
    };

Sortable_list.h

typedef Key Record;
class Sortable_list:public List<Record>
{
void selection_sort()
    {
        for(int position=count-1;position>0;i--) // Count is not declared in the scope
        {
        int max=max_key(0, position);
        swap(max, position);
        }
    }
};

The error is mentioned within the comments. Here's the full code of List.h : http://pastebin.com/3xTADqvN[^]
Sortable_list.h: http://pastebin.com/k1ARsyCR[^]

Posted 11-Jan-11 5:55am

optimus_prime1

Updated 11-Jan-11 6:32am

User 7429338

v3

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#realJSOP 11-Jan-11 12:03pm

What does your constructor look like?

optimus_prime1 11-Jan-11 12:07pm

List():count(0){}
Link to full code is in the post above

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Aescleal · Answer 1 · 2011-01-11T07:21:00

Just leaving aside the whole "protected data members are the sperm of the devil" thing, the code you've presented there looks like it should compile.

The only suggestion I can make based on the code is that you haven't included something - I couldn't see any mention of #include "List.h" in your sortable list header - or you've got two different headers kicking around.

Going forward the best thing to do (apart from not trying to implement your own list) is to start again on the derived class. Take it baby steps, adding small bits of code each time. Then when something goes wrong you know what you did to cause it and can hopefully isolate and fix it. Just start with something simple:

#include "List.h"

class A : public List<int>
{
    public:
        A()
        {
            count = 87;
        }
};

If that compiles and works with no additional headers aside from the base class then you know your problem is with something else. If it doesn't then there's something weird with the base class, but cunningly disguised.

Cheers,

Ash

PS: Or after seeing the error messages it could be the loop variable...

Sergey Alexandrovich Kryukov · Answer 2 · 2011-01-11T06:59:00

Solution 1

optimus_prime1, glad to hear from you again.

I just compiled your code -- it does compile.

[EDIT]: see comments below.

Posted 11-Jan-11 6:59am

Sergey Alexandrovich Kryukov

Updated 11-Jan-11 8:09am

v2

Comments

optimus_prime1 11-Jan-11 13:23pm

If it would have been compiling for me, I wouldn't have been asking this. Screenshot: http://i.imgur.com/bc2mx.jpg

Aescleal 11-Jan-11 13:28pm

Try fixing some of the other errors - the one that says i isn't defined could be confusing the compiler.

optimus_prime1 11-Jan-11 13:30pm

@Aescleal: Just did that but to no avail. Screenshot: http://i.imgur.com/A9KAs.jpg

Aescleal 11-Jan-11 13:33pm

I completely missed the fact you're not guarding your include files with include guards to prevent redefinition.

http://en.wikipedia.org/wiki/Include_guard describes how to use them fairly well.

Sergey Alexandrovich Kryukov 11-Jan-11 14:06pm

@Aescleal: this is a good point, I've missed it, too as I compiled all together -- in a write way. "Include" Must die.

Sergey Alexandrovich Kryukov 11-Jan-11 14:08pm

@optimus_prime1: you should have an answer by now. Sorry for my rant, I'll remove it.
(However, inaccurate include is your fault anyway.)

optimus_prime1 11-Jan-11 14:21pm

I put up the include guards but the protected memebers are shown still out of scope. Screencap: http://i.imgur.com/x2NcJ.jpg

Espen Harlinn 11-Jan-11 14:26pm

5+ for patience ...

Sergey Alexandrovich Kryukov 11-Jan-11 14:59pm

Thank you, Espen.
My patience is still under the probation :-)

Sergey Alexandrovich Kryukov 11-Jan-11 15:37pm

@optimus_prime1: well, check up again... I put both classes in one file and it compiled (you may want to try doing so as your starting point) => if you put them in two different files in a proper way in different files. Anyway, there is nothing wrong with your visibility of class members (I know C++ compiler messages can be misleading. "Include" must die together with C++.)

Rajesh Katalkar · Answer 3 · 2011-01-11T16:39:00

you are using code blocks.
you must be using gcc.
have you added some other libraries.
i think the other library is having the List template class which is used in place of yours.

put these statements in ur List.h before the start and end of ur file

#ifndef _MYLIST_H
#define _MYLIST_H

...ur code

#endif

in ur Sortable_list.h

#include "List.h" //note very important
#ifndef _SORTLIST_H
#define _SORTLIST_H

ur code......

#endif

regards
rajesh

Unable to inherit protected variables

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