Question about derived class member function call

[fl]

Hi,

When I run the following code, I am puzzled about

















...............
#include <iostream>
using namespace std;

struct BaseConstructor
{
BaseConstructor(int=0)
{}
};

class RealNumber;
class Complex;
class Number;
class Number
{
friend class RealNumber;
friend class Complex;
public:
Number ();
Number & operator = (const Number &n);
Number (const Number &n);
virtual ~Number();
virtual Number operator + (Number const &n) const;
void swap (Number &n) throw ();

static Number makeReal (double r);
static Number makeComplex (double rpart, double ipart);
protected:
Number (BaseConstructor);

private:
void redefine (Number *n);
virtual Number complexAdd (Number const &n) const;
virtual Number realAdd (Number const &n) const;

Number *rep;
short referenceCount;
};

class Complex : public Number
{
friend class RealNumber;
friend class Number;

Complex (double d, double e);
Complex (const Complex &c);
virtual ~Complex ();

virtual Number operator + (Number const &n) const;
virtual Number realAdd (Number const &n) const;
virtual Number complexAdd (Number const &n) const;
double rpart, ipart;
};

class RealNumber : public Number
{
friend class Complex;
friend class Number;

RealNumber (double r);
RealNumber (const RealNumber &r);
virtual ~RealNumber ();

virtual Number operator + (Number const &n) const;
virtual Number realAdd (Number const &n) const;
virtual Number complexAdd (Number const &n) const;

double val;
};

/// Used only by the letters.
Number::Number (BaseConstructor): rep (0), referenceCount (1)
{
cout << "rep(0), referenceCount(1)\n" << rep << ", " << referenceCount << endl;
}

/// Used by user and static factory functions.
Number::Number () : rep (0), referenceCount (0)
{}

/// Used by user and static factory functions.
Number::Number (const Number &n): rep (n.rep), referenceCount (0)
{
cout << "Constructing a Number using Number::Number\n";
if (n.rep)
n.rep->referenceCount++;
}

Number Number::makeReal (double r)
{
Number n;
n.redefine (new RealNumber (r));
return n;
}

Number Number::makeComplex (double rpart, double ipart)
{
Number n;
n.redefine (new Complex (rpart, ipart));
return n; // nCaller
}

int main (void)
{
Number::makeComplex (1, 2);
cout << "Finished\n";
return 0;
}

[fl]

Hi,
Excuse me for accidentally post the incomplete message previously.
In main(), line

Number::makeComplex (1, 2);

calls

Number Number::makeComplex (double rpart, double ipart)

Then, it calls constructor:

Number::Number () : rep (0), referenceCount (0)

Next, it calls

Complex::Complex (double d, double e) : Number (BaseConstructor()),
rpart (d), ipart (e)
{
cout << "Constructing a Complex\n";
}

Next, it calls Complex constructor:
Complex::Complex (double d, double e) : Number (BaseConstructor()),
rpart (d), ipart (e)

Next, it calls member function:
void Number::redefine (Number *n)

My question comes here. When it runs line
return n; // nCaller

It calls constructor:

Number::Number (const Number &n): rep (n.rep), referenceCount (0)

I don't understand why it calls the above constructor.

For your reference, here is the console window message:


rep(0), referenceCount(1)
00000000, 1
Constructing a Complex

Constructing a Number using Number::Number

I think that I have not enought understanding on class inheritance.
Hopefully, the answer for this question can teach me some.
Can you help me out?

Thanks,

[Melzzzzz]

On Mon, 15 Jun 2015 19:59:16 -0700 (PDT)
fl <rxj...@gmail.com> wrote:

> Hi,
>
> When I run the following code, I am puzzled about
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>
> ...............
> #include <iostream>
> using namespace std;
>
> struct BaseConstructor
> {
> BaseConstructor(int=0)
> {}
> };
>

I am puzzled buy this, too...

[Richard]

[Please do not mail me a copy of your followup]

fl <rxj...@gmail.com> spake the secret code
<5008983f-f182-449b...@googlegroups.com> thusly:

>struct BaseConstructor
>{
> BaseConstructor(int=0)
> {}
>};

Didn't we already go over this in another thread?

It feels like a bunch of people are taking a summer course in C++ using
a confusing and poorly written book and the instructor has recommended
you come here for help.
--
"The Direct3D Graphics Pipeline" free book <http://tinyurl.com/d3d-pipeline>
The Computer Graphics Museum <http://computergraphicsmuseum.org>
The Terminals Wiki <http://terminals.classiccmp.org>
Legalize Adulthood! (my blog) <http://legalizeadulthood.wordpress.com>