behaviour of const_cast

Question

I was reading about const_cast operator in c++

1.First weird thing thing i can\'t understand is

const_cast operator syntax i.e.

<

Answer 1

it helps to cast away constness of an expression of type Type

No, Type is the type of the result, not the type of the operand.

What i think is const of this pointer should be casted away

this has type const ConstTest*. const_cast<ConstTest*>(this) has type ConstTest*. That's what "casting away const" from a pointer-to-const means.

I feel code should have been ConstTest *c = const_cast<ConstTest>(*this)

The result of const_cast<T> has type T, that's how it's defined. Maybe you would have defined it differently, but tough luck, you don't get a ConstTest* by writing const_cast<ConstTest>, you get it by writing const_cast<ConstTest*>. Your preferred syntax is not available.

You can either do ConstTest &c = const_cast<ConstTest&>(*this) or ConstTest *c = const_cast<ConstTest*>(this), so pick your favorite.

The result of a const_cast expression is an rvalue unless Type is a reference type. In this case, the result is an lvalue.

why so and why it is not true in case of pointers?

It is true of pointers. ConstTest* is not a reference type, and the result of const_cast<ConstTest*>(this) is an rvalue. You then assign that value to the variable c.