> Invariants are functions that run at the start and end of every public member function, and can be used to ensure that the type is always in a valid state.
The ironic thing about this is that it means that the public functions of an object can't, generally, call each other willy-nilly unless they take special precautions: very often, the object's invariants are broken when the execution is in a middle of the object's method. This is not a problem with D, the language merely helps you to uncover this lurking problem which usually simply goes unnoticed until something breaks and someone notices it.
The ironic thing about this is that it means that the public functions of an object can't, generally, call each other willy-nilly unless they take special precautions: very often, the object's invariants are broken when the execution is in a middle of the object's method. This is not a problem with D, the language merely helps you to uncover this lurking problem which usually simply goes unnoticed until something breaks and someone notices it.