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a problem with an program

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  a problem with an program karam hello <karamhello2@gmail.com> - 2023-09-29 12:59 -0700
    Re: a problem with an program Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-09-29 21:13 +0100
      Re: a problem with an program "Alf P. Steinbach" <alf.p.steinbach@gmail.com> - 2023-10-01 16:00 +0200
        Re: a problem with an program Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-10-01 16:29 +0100
        Re: a problem with an program Ben Bacarisse <ben.usenet@bsb.me.uk> - 2023-10-04 01:56 +0100
    Re: a problem with an program David Brown <david.brown@hesbynett.no> - 2023-09-30 16:57 +0200

#92250 — a problem with an program

 i have a problem with this program using C++ OOP inheritance specially on class c:
#include <iostream>
using namespace std;
class a{ 
    private:
        string name;
        int age;
    public:
        a(string n, int a){
            name = n;
            age = a;
        }
};
class b{
    private:
        string email;
    public:
        b(string em){
            email = em;
        }
};
class c:public a, public b{
    public:
        c(string n, int a, string em) : a(n, a), b(em){}
};
int main(){
    c c1("k", 10, "com");
}

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#92252

karam hello <karamhello2@gmail.com> writes:

>  i have a problem with this program using C++ OOP inheritance
>  specially on class c:

Your compiler should be telling your what's wrong.  It might not do so
very clearly, but it should be pointing you to where the problem is.

But let me play compiler here and give you a different error message...

> #include <iostream>
> using namespace std;
> class a{ 
>     private:
>         string name;
>         int age;
>     public:
>         a(string n, int a){
>             name = n;
>             age = a;
>         }
> };
> class b{
>     private:
>         string email;
>     public:
>         b(string em){
>             email = em;
>         }
> };
> class c:public a, public b{
>     public:
>         c(string n, int a, string em) : a(n, a), b(em){}
line 23 position 41 ______________________^
a is an int.  I can't call a(n, a) when a is an int.

> };
> int main(){
>     c c1("k", 10, "com");
> }

Does that help?

-- 
Ben.

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#92288

On 2023-09-29 10:13 PM, Ben Bacarisse wrote:
> karam hello <karamhello2@gmail.com> writes:
> 
>>   i have a problem with this program using C++ OOP inheritance
>>   specially on class c:
> 
> Your compiler should be telling your what's wrong.  It might not do so
> very clearly, but it should be pointing you to where the problem is.
> 
> But let me play compiler here and give you a different error message...
> 
>> #include <iostream>
>> using namespace std;
>> class a{
>>      private:
>>          string name;
>>          int age;
>>      public:
>>          a(string n, int a){
>>              name = n;
>>              age = a;
>>          }
>> };
>> class b{
>>      private:
>>          string email;
>>      public:
>>          b(string em){
>>              email = em;
>>          }
>> };
>> class c:public a, public b{
>>      public:
>>          c(string n, int a, string em) : a(n, a), b(em){}
> line 23 position 41 ______________________^
> a is an int.  I can't call a(n, a) when a is an int.
> 
>> };
>> int main(){
>>      c c1("k", 10, "com");
>> }
> 
> Does that help?

g++ complains about that thing, but Visual C++ compiles the code just 
fine as C++17.

Sort of, Visual C++ is consistent (base classes treated the same as data 
members), while g++ is conforming. They're both "con". Just differently.

I guess learning point is, to be both consistent and conforming never 
choose the same name for a constructor parameter and sub-object.


- Alf

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#92289

"Alf P. Steinbach" <alf.p.steinbach@gmail.com> writes:

> On 2023-09-29 10:13 PM, Ben Bacarisse wrote:
>> karam hello <karamhello2@gmail.com> writes:
>> 
>>>   i have a problem with this program using C++ OOP inheritance
>>>   specially on class c:
>> Your compiler should be telling your what's wrong.  It might not do so
>> very clearly, but it should be pointing you to where the problem is.
>> But let me play compiler here and give you a different error message...
>> 
>>> #include <iostream>
>>> using namespace std;
>>> class a{
>>>      private:
>>>          string name;
>>>          int age;
>>>      public:
>>>          a(string n, int a){
>>>              name = n;
>>>              age = a;
>>>          }
>>> };
>>> class b{
>>>      private:
>>>          string email;
>>>      public:
>>>          b(string em){
>>>              email = em;
>>>          }
>>> };
>>> class c:public a, public b{
>>>      public:
>>>          c(string n, int a, string em) : a(n, a), b(em){}
>> line 23 position 41 ______________________^
>> a is an int.  I can't call a(n, a) when a is an int.
>> 
>>> };
>>> int main(){
>>>      c c1("k", 10, "com");
>>> }
>> Does that help?
>
> g++ complains about that thing, but Visual C++ compiles the code just fine
> as C++17.

Curious.  Which one is correct?  Without studying the standard, I would
have thought that gcc has it right.

-- 
Ben.

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#92348

"Alf P. Steinbach" <alf.p.steinbach@gmail.com> writes:

> On 2023-09-29 10:13 PM, Ben Bacarisse wrote:
>> karam hello <karamhello2@gmail.com> writes:
>> 
>>>   i have a problem with this program using C++ OOP inheritance
>>>   specially on class c:
>> Your compiler should be telling your what's wrong.  It might not do so
>> very clearly, but it should be pointing you to where the problem is.
>> But let me play compiler here and give you a different error message...
>> 
>>> #include <iostream>
>>> using namespace std;
>>> class a{
>>>      private:
>>>          string name;
>>>          int age;
>>>      public:
>>>          a(string n, int a){
>>>              name = n;
>>>              age = a;
>>>          }
>>> };
>>> class b{
>>>      private:
>>>          string email;
>>>      public:
>>>          b(string em){
>>>              email = em;
>>>          }
>>> };
>>> class c:public a, public b{
>>>      public:
>>>          c(string n, int a, string em) : a(n, a), b(em){}
>> line 23 position 41 ______________________^
>> a is an int.  I can't call a(n, a) when a is an int.
>> 
>>> };
>>> int main(){
>>>      c c1("k", 10, "com");
>>> }
>> Does that help?
>
> g++ complains about that thing, but Visual C++ compiles the code just fine
> as C++17.

Curious.  Which one is correct I wonder.

-- 
Ben.

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#92261

On 29/09/2023 21:59, karam hello wrote:
>   i have a problem with this program using C++ OOP inheritance specially on class c:
> #include <iostream>
> using namespace std;
> class a{
>      private:
>          string name;
>          int age;
>      public:
>          a(string n, int a){
>              name = n;
>              age = a;
>          }
> };
> class b{
>      private:
>          string email;
>      public:
>          b(string em){
>              email = em;
>          }
> };
> class c:public a, public b{
>      public:
>          c(string n, int a, string em) : a(n, a), b(em){}
> };
> int main(){
>      c c1("k", 10, "com");
> }

It looks like you are learning the language.  I recommend getting in the 
habit of using good names for your classes (and everything else), rather 
than "a" or "b".  Good naming makes code easier to write, and vastly 
easier to read, and you should practice it from the start, even for 
simple test code.  See if it helps you out here.

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