|This rule is Obsolete|
|Synopsis:||Do not let const member functions change the state of the program|
Note that const member functions are allowed to change e.g. mutable members (see also [CON#005]). Similarly, member functions might modify an internal cache in order to achieve significant performance improvements. Such an optimization could be completely shielded from the rest of the program, and it must be allowed to call such a function for const objects. Hence it must be allowed to be declared as a const function.
See also [INT#006].