Types of constructors

[Sathyaish]

What is a private constructor, and why would a class have one? What are
the other kinds of constructors besides:

(1) public constructors; and
(2) parameterized constructors

And I understand that they are not mutually exclusive of one another.
The above classification assimilates my knowledge of having used
constructors in both the above manners.

[Rolf Magnus]

Sathyaish wrote:

What is a private constructor,
It's a constructor that is declared in a private section of a class.
and why would a class have one?
Because it might not want other classes to be able to create instances of
it.
What are the other kinds of constructors besides:

(1) public constructors; and
(2) parameterized constructors

And I understand that they are not mutually exclusive of one another.

Just like any member, a constructor can be public, protected or private. And
just like normal member functions it can have parameters or not.

There is a special kind of constructors, the conversion constructors. A
constructor that can be called with exactly one argument is considered a
conversion constructor, used to convert the parameter type into the class
the constructor belongs to.
And there is a special kind of conversion constructors, the copy
constructor. It is used to create a copy of an existing object of the same
class. Even though both classes are the same, it counts as a conversion
constructor.

[Sathyaish]

That is a treasure, Rolf. Thank you so very much.

I understood every bit of it. I want some more. Can you please provide
me some simple, easy-to-understand code snippets for conversion
constructors and copy constructors?

[Mike Wahler]

"Sathyaish" <Sa*******@Yahoo.com> wrote in message
news:11**********************@f14g2000cwb.googlegr oups.com...

That is a treasure, Rolf. Thank you so very much.

I understood every bit of it. I want some more. Can you please provide
me some simple, easy-to-understand code snippets for conversion
constructors and copy constructors?

class A
{
public:
/* 'conversion constructor': */
/* converts a type 'int' object */
/* to a type 'A' object */
A(int)
{
}

/* 'copy constructor': */
/* creates a copy of an existing */
/* type 'A' object */
A(const A& a)
{
}
};

int main()
{
int i(0);

A a1(i); /* creates type 'A' object by */
/* converting from type 'int' object 'i' */
/* (calls constructor 'A::A(int) )' */

A a2(a1); /* creates a copy of type 'A' object 'a1' */
/* (calls constructor 'A::A(const A&) )' */

return 0;
}

-Mike

[Sathyaish]

Thanks very much, Mike. I understood it a lot better with that little
snippet.