Hi, Trying to find some good docs on QuickCheck, if anyone has one ? Been scanning what I can find, but a question. What would be the best way to generate two different/distinct integers ? Use arbitrary ( if so do you have an example ) or a conditional on the property. Though I read the later can reduce passing test count. Thanks Graham
On Mon, Nov 12, 2012 at 07:21:06PM +0000, graham <at> fatlazycat.com wrote:
> Hi,
>
> Trying to find some good docs on QuickCheck, if anyone has one ?
>
> Been scanning what I can find, but a question.
>
> What would be the best way to generate two different/distinct integers ?
I would use Quickcheck's implication operator here:
quickCheck $ \x y -> x /= (y :: Int) ==> ...
Cheers,
Simon
On Mon, Nov 12, 2012 at 10:14:30PM +0100, Simon Hengel wrote:
> On Mon, Nov 12, 2012 at 07:21:06PM +0000, graham <at> fatlazycat.com wrote:
> > Hi,
> >
> > Trying to find some good docs on QuickCheck, if anyone has one ?
> >
> > Been scanning what I can find, but a question.
> >
> > What would be the best way to generate two different/distinct integers ?
>
> I would use Quickcheck's implication operator here:
>
> quickCheck $ \x y -> x /= (y :: Int) ==> ...
That's good, but it only eliminates test cases after they have been
generated. A slightly better (IMHO) version is to generate "correct"
values in the first place:
prop_Test :: Property
prop_Test =
forAll (arbitrary::Gen Int) $ \x ->
forAll (arbitrary `suchThat` (/= x)) $ \y ->
…
regards,
iustin
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(Continue reading)
Thanks, will try them both. With regards to the implication I assume it's just regarded as one property test ? To get two values greater than zero I have something like prop_something x y = .......do blah with positive integers ==> x > 0 && y > 0 But my test fails as it appears to be injecting a negative number and the test fails. But the implication does not cause the failed test to be ignored. Must be missing something ??? Thanks On Mon, Nov 12, 2012, at 10:00 PM, Iustin Pop wrote: > On Mon, Nov 12, 2012 at 10:14:30PM +0100, Simon Hengel wrote: > > On Mon, Nov 12, 2012 at 07:21:06PM +0000, graham <at> fatlazycat.com wrote: > > > Hi, > > > > > > Trying to find some good docs on QuickCheck, if anyone has one ? > > > > > > Been scanning what I can find, but a question. > > > > > > What would be the best way to generate two different/distinct integers ? > > > > I would use Quickcheck's implication operator here: > > > > quickCheck $ \x y -> x /= (y :: Int) ==> ...(Continue reading)
Thanks, will try them both. With regards to the implication I assume
it's just regarded as one property test ?
To get two values greater than zero I have something like
prop_something x y = .......do blah with positive integers
==> x > 0 && y > 0
But my test fails as it appears to be injecting a negative number and
the test fails. But the implication does not cause the failed test to be
ignored.
Must be missing something ???
Thanks
On Mon, Nov 12, 2012, at 10:00 PM, Iustin Pop wrote:
> On Mon, Nov 12, 2012 at 10:14:30PM +0100, Simon Hengel wrote:
> > On Mon, Nov 12, 2012 at 07:21:06PM +0000, graham <at> fatlazycat.com wrote:
> > > Hi,
> > >
> > > Trying to find some good docs on QuickCheck, if anyone has one ?
> > >
> > > Been scanning what I can find, but a question.
> > >
> > > What would be the best way to generate two different/distinct integers ?
> >
> > I would use Quickcheck's implication operator here:
> >
> > quickCheck $ \x y -> x /= (y :: Int) ==> ...
>
> That's good, but it only eliminates test cases after they have been
> generated. A slightly better (IMHO) version is to generate "correct"
> values in the first place:
>
> prop_Test :: Property
> prop_Test =
> forAll (arbitrary::Gen Int) $ \x ->
> forAll (arbitrary `suchThat` (/= x)) $ \y ->
> …
>
> regards,
> iustin
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http://www.haskell.org/mailman/listinfo/haskell-cafe
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prop_something x y = .......do blah with positive integers
==> x > 0 && y > 0
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hi,
On 13 November 2012 21:52, <graham <at> fatlazycat.com> wrote:
prop_something x y = .......do blah with positive integers
==> x > 0 && y > 0
quickcheck provides a few nice new types for such cases. try:
prop_something (Positive x) (Positive y) = ...
this way qc only generates positive numbers, instead of generating and discarding some.
hth,
--
Ozgur Akgun
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