[Haskell-cafe] is proof by testing possible?
Joe Fredette
jfredett at gmail.com
Mon Oct 12 13:48:55 EDT 2009
In general? No- If we had an implementation of the `sin` function, how
can testing a finite number of points along it determine
if that implementation is correct for every point?
For specific functions (particularly those with finite domain), it is
possible. If you know the 'correct' output of every input, then
testing each input and ensuring correct output will work. Consider the
definition of the `not` function on booleans. The domain only has two
elements (True and False) and the range has only two outputs (True and
False), so if I test every input, and insure it maps appropriately to
the specified output, we're all set.
Basically, if you can write your function as a big case statement that
covers the whole domain, and that domain is finite, then the function
can be tested to prove it's correctness.
Now, I should think the Muad'Dib would know that, perhaps you should
go back to studying with the Mentats. :)
/Joe
On Oct 12, 2009, at 1:42 PM, muad wrote:
>
> Is it possible to prove correctness of a functions by testing it? I
> think the
> tests would have to be constructed by inspecting the shape of the
> function
> definition.
>
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