if a method is overloaded with a const version, in the case thateither one is okay, which shall the compiler pick?

[yuyang08]

Dear all,

I have a question on the const methods. If a method is overloaded with
a const version, in the case that either one is okay (for example, the
following code), which shall the compiler pick? Could you tell which
section of the C++ standard specifies this?

Many thanks!

-Andy

#include <iostream>
using namespace std;

class A{
public:
int foo() const { return 6; }
int foo() { return 5; }
public:
int x;
};

int main()
{
A ca;
int c = ca.foo();
cout << "c = " << c << endl;
return 0;
}

[Pete Becker]

On 2008-10-26 14:53:09 -0400, yu******@gmail. com said:

I have a question on the const methods. If a method is overloaded with
a const version, in the case that either one is okay (for example, the
following code), which shall the compiler pick? Could you tell which
section of the C++ standard specifies this?

It's simply <ga matter of overload resolution.

#include <iostream>
using namespace std;

class A{
public:
int foo() const { return 6; }
int foo() { return 5; }
public:
int x;
};

int main()
{
A ca;
int c = ca.foo();
cout << "c = " << c << endl;
return 0;
}

The first version of A::foo takes a this pointer of type const A*; the
second one takes a this pointer of type A*. At the point of the call,
ca is not const, so the this pointer that the compiler generates has
type A*, and the call goes to the second version of A::foo. If that
version hadn't been defined, the call would go to the remaining (const)
version after a conversion of the type of the this pointer argument
from A* to const A*.

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)

[Pete Becker]

On 2008-10-26 15:18:27 -0400, Pete Becker <pe**@versatile coding.comsaid:

On 2008-10-26 14:53:09 -0400, yu******@gmail. com said:

>I have a question on the const methods. If a method is overloaded with
a const version, in the case that either one is okay (for example, the
following code), which shall the compiler pick? Could you tell which
section of the C++ standard specifies this?

It's simply <ga matter of overload resolution.

>#include <iostream>
using namespace std;

class A{
public:
int foo() const { return 6; }
int foo() { return 5; }
public:
int x;
};

int main()
{
A ca;
int c = ca.foo();
cout << "c = " << c << endl;
return 0;
}

The first version of A::foo takes a this pointer of type const A*; the
second one takes a this pointer of type A*. At the point of the call,
ca is not const, so the this pointer that the compiler generates has
type A*, and the call goes to the second version of A::foo. If that
version hadn't been defined, the call would go to the remaining (const)
version after a conversion of the type of the this pointer argument
from A* to const A*.

Whoops, that's a bit ambiguous. The last sentence should start with "If
that version hadn't been declared," That is:

class A {
public:
int foo() const;
};

--
Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)