On Saturday, 4 November 2017 at 16:57:50 UTC, Adam D. Ruppe wrote:
On Saturday, 4 November 2017 at 15:27:39 UTC, Ola Fosheim
Grøstad wrote:
No, Jonathan is correct. The postcondition should be able to
access values as they were stated in the precondition.
Yes, they should be able to access values, but D's limitations
on this doesn't make them useless or replaced by unittests.
They do a different job than unittests.
But then they do a job that subtyping does better…? So why do
this with "contracts"?
Anyhow, I think the ideal for contracts in terms of debugging is
to express postconditions in terms of public interface rather
than internal representation, e.g. for a stack push:
oldthis.size() + 1 == newthis.size() // or length() or whatever
the interface provides
Then hammer the interface in unit tests rather than writing the
explicit test in the unit test itself. (e.g. the unit test does
not have to know the conditions, just explore a wide range of
configurations).
