Andrei Alexandrescu wrote:
If a function throws a class inheriting Error but not Exception (i.e. an
unrecoverable error), then the postcondition doesn't need to be satisfied.
I just realized that postconditions, however, must be satisfied if the
function throws an Exception-derived object. There is no more return
value, but the function must leave everything in a consistent state. For
example, a function reading text from a file may have the postcondition
that it closes the file, even though it may throw a malformed file
exception.
This may sound crazy, but if you just follow the facts that distinguish
regular error handling from program correctness, you must live with the
consequences. And the consequence is - a function's postcondition must
be designed to take into account exceptional paths. Only in case of
unrecoverable errors is the function relieved of its duty.
Andrei
Isn't the post-condition mainly to assert the correctness of the return
value? Or at least partially? The output cannot be correct if an
exception is thrown, so any assertion in the post condition concerning
the output would fail by definition, right?
I would say the invariant() is the correct part to run.
