Operator overload ostream

[Lio]

Hi, I dont know how to do operator overload for object with only array of 10 integers
Thanks

ostream& operator<<(ostream& out,MyObj & o)
    {
        for(int i;i<s;++i)
        out<<o.array[i]<<" ";
        return out;
    }

[ne555]

¿So what is the problem with that?

[Lio]

I dont know how to do it right,it gives me error that ostream must take exactly one argument

[ne555]

Could you please copy-paste the error, and the offending lines (with a little context)

By the way ostream& operator<<(ostream& out, const MyObj & o) you don't want to modify the object, ¿right?

[Lio]

No I dont modify the object
And the object is array of ten integers ,s is the size of the array


practice.cpp|20|error: 'std::ostream& MyObj::operator<<(std::ostream&, MyObj&)' must take exactly one argument|
\practice.cpp||In member function 'MyObj& MyObj::operator+(MyObj&)':|
practice.cpp|29|warning: reference to local variable 'temp' returned [enabled by default]|
||=== Build finished: 1 errors, 1 warnings ===|

[cire]

If you're defining operator<< in your class you would do so like:

ostream& operator<<(ostream& o) const
{
          for (int i=0; i<s; ++i)
                    o << array[i] << " " ;
          return o;
}

then if you want to use it in the normal way, you'll also need a helper function outside the class definition:

inline ostream& operator<<(ostream&out, const MyObj& o)
{
          return o.operator<<(out) ;
}

Alternatively you can skip the definition of operator<< in the class and make the stand-alone function a friend of MyObj.

[Lio]

Thanks
I copy and paste your code but the error is the same

[ne555]

o.operator<<(out); kind of defeats the purpose of operator overloading, ¿don't you think?

cire wrote:

you'll also need a helper function outside the class definition: ostream& operator<<(ostream&out, const MyObj& o);
you can skip the definition of operator<< in the class and make the stand-alone function a friend

[cire]

Supplying an overload defeats the purpose of operator overloading? No, I don't think so.

[ciphermagi]

You have to skip the operator overloading the class and make it a friend.

You can't add methods to the ostream/istream classes, so you make them global friends:

friend ostream& operator<<(ostream& out, const myObj& obj);

[ne555]

@cire:
I meant that you don't use operators like o.operator<<(out);
You will simply o << out;

[cire]

Why don't you? It's more clear than o << out. You aren't inserting out into o. All we were doing was forwarding to our overloaded class operator, and that's much clearer with an explicit call.

[ne555]

Then we will better with o.print_at(out);
Make the operators intuitive.
Don't change their semantic.

[cire]

This is entirely a matter of style. No semantics were changed.

I would simply skip the member operator and go with the stand-alone. print_at is an inaccurate description. out could be a file stream, a console stream, a stringstream. Conceptually, we're inserting data into a stream, so if I went the named method route, I'd be more likely to use insert(out) taking an output iterator as the parameter type.