[Haskell-cafe] the purpose of QuickCheck's size parameter

[Oliver Charles]

Is SmallCheck more principles in this regard, or would people consider that
equally hacky?

On Sun, 17 Jun 2018, 10:18 am Petr Pudlák, <petr.mvd at gmail.com> wrote:

> PS: Just to make clear, it's not that I have something against QuickCheck
> or similar libraries, on the contrary, they're great! I'm just playing the
> devil's advocate to analyze and understand the concept.
>
> ne 17. 6. 2018 v 4:05 odesílatel Oleg Grenrus <oleg.grenrus at iki.fi>
> napsal:
>
>> Not only avoid extremely large trees, but in general guarantee
>> termination of the generation process
>>
>> Sent from my iPhone
>>
>> On 15 Jun 2018, at 0.31, David Feuer <david.feuer at gmail.com> wrote:
>>
>> data Foo a = Leaf a | Node [Foo a]
>>
>> Without the size parameter, it's a bit tricky to control the distribution
>> to avoid generating extremely large trees. I certainly agree, however, that
>> the size parameter is an ugly and ill-specified hack.
>>
>> On Thu, Jun 14, 2018, 4:20 PM Petr Pudlák <petr.mvd at gmail.com> wrote:
>>
>>> Hi everyone,
>>>
>>> I'd like to better understand the principles behind the 'size'
>>> parameter. Looking at quickCheckWithResult [1], its computation seems to be
>>> somewhat non-trivial, or even arbitrary. As far as I understand it, the
>>> size is varied throughout tests, increasing from small to larger values. I
>>> see two main purposes:
>>>
>>> - Test on smaller as well as larger values. But with generators having
>>> proper distribution of values, this should happen anyway, just as if we had
>>> a constant, larger 'size' parameter.
>>> - Starting with smaller sizes allows to find smaller count-examples
>>> first. But with shrinking, it doesn't matter that much, big
>>> counter-examples are shrunk to smaller ones anyway in most cases.
>>>
>>> So is this parameter actually necessary? Would anything change
>>> considerably if it was dropped?
>>>
>>> Thanks,
>>> Petr
>>>
>>> [1]
>>> http://hackage.haskell.org/package/QuickCheck-2.11.3/docs/src/Test-QuickCheck-Test.html#quickCheckWithResult
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