[Haskell-cafe] derive + quickCheck

[bob zhang]

Hi,
    thank you .
    I read your souce, I found the depth is only 2, right?
   like data A = [A]|String, any easy way to control the maximum_depth 
of generated data?

Regards,bob
于 11-7-17 下午8:13, Ivan Lazar Miljenovic 写道:
> On 17 July 2011 23:42, bob zhang<bobzhang1988 at gmail.com>  wrote:
>> Hi, all,
>> I found derive + quickCheck very useful but I came across some problems.
>> I used derive to derive instance of Arbitrary immeditaely, but sometimes the
>> sample is non-terminating, which I mean the result is very very big.
>>
>> [snip]
>>
>> data JValue = JString String
>> | JNumber Double
>> | JBool Bool
>> | JNull
>> | JObject [(String, JValue)] --
>> | JArray [JValue] --
>> deriving (Eq,Ord,Show)
>> $(derive makeArbitrary ''JValue)
> Your JValue type is recursive; as such I highly suggest you manually
> create the Arbitrary instances for it (e.g. a helper function with a
> Bool parameter to indicate whether or not to create recursive calls;
> see how I do it in
> http://code.haskell.org/graphviz/Data/GraphViz/Testing/Instances/Canonical.hs
> where the DotStatements type can have DotSubGraph values, which in
> turn have DotStatements).
>