On Wed, Sep 26, 2018 at 6:37 PM Chris Angelico <ros...@gmail.com> wrote:
>
> On Wed, Sep 26, 2018 at 5:51 PM Marko Ristin-Kaufmann
> <marko.ris...@gmail.com> wrote:
> >
> > Hi Chris,
> >
> >> It's easy to say that they're boolean expressions. But that's like
> >> saying that unit tests are just a bunch of boolean expressions too.
> >> Why do we have lots of different forms of test, rather than just a big
> >> fat "assert this and this and this and this and this and this"?
> >> Because the key to unit testing is not "boolean expressions", it's a
> >> language that can usefully describe what it is we're testing.
> >> Contracts aren't just boolean expressions - they're a language (or a
> >> mini-language) that lets you define WHAT the contract entails.
> >
> >
> > Sorry, I misunderstood you. You are probably referring to knowing the terms
> > like "preconditions, postconditions, invariants, strengthening/weakening",
> > right? In that case, yes, I agree, I presuppose that readers are familiar
> > with the concepts of DbC. Otherwise, of course, it makes no sense to use
> > DbC if you assume nobody could actually figure out what it is :).
> >
>
> Let's say you want to define a precondition and postcondition for this
> function:
>
> def fibber(n):
> return n < 2 ? n : fibber(n-1) + fibber(n-2)
Uhhhhhhhh....
def fibber(n):
return n if n < 2 else fibber(n-1) + fibber(n-2)
Let's, uhh, pretend that I didn't just mix languages there.
For the original, we can say:
@post(raises=ProgrammerFailedSanCheckError)
ChrisA
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