Calling the ``++not++`` or ``++~++`` prefix operator twice might be redundant: the second invocation undoes the first. Such mistakes are typically caused by accidentally double-tapping the key in question without noticing. Either this is a bug, if the operator was actually meant to be called once, or misleading if done on purpose.
Calling ``++not++`` twice is commonly done instead of using the dedicated "bool()" builtin function. However, the latter one increases the code readability and should be used.
If the ``++~++`` function has been overloaded in a customised class and has been called twice, no warning is raised as it is assumed to be an expected usage.
