const member functions

[Denver Dash]

Hi. I heard once that there is a way to allow a const member function to
alter the value of a member if the member is declared in some way. Can
someone tell me how to do that, or is this impossible?

For example:

class foo
{
specialdeclaration int index;
void bar() const
{
index = 0; \\ ok because index has been declared in a special way.
}
};

thanks,
denver.

 

[Thomas Wintschel]

Hi. I heard once that there is a way to allow a const member function to
alter the value of a member if the member is declared in some way. Can
someone tell me how to do that, or is this impossible?

For example:

class foo
{
specialdeclaration int index;
void bar() const
{
index = 0; \\ ok because index has been declared in a special way.
}
};

thanks,
denver.

mutable

 

[Ron Natalie]

mutable

Yes, but you must be very careful NEVER to actually make an const foo. This is
a problem with trying to use mutable.

const foo x;

x.bar(); // well formed, but undefined behavior.

 

[Christoph Rabel]

Yes, but you must be very careful NEVER to actually make an const foo. This is
a problem with trying to use mutable.

const foo x;

x.bar(); // well formed, but undefined behavior.

No.

See 7.1.5.1.
Its perfectly save to modify a mutable member of a const object.

mfg

Christoph