On 19 July 2011 21:23, bob zhang wrote:

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?

You could always use an Int parameter instead of a Bool and have it count down to 0, in which case you stop generating recursive structures.

Regards,bob 于 11-7-17 下午8:13, Ivan Lazar Miljenovic 写道:

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On 17 July 2011 23:42, bob zhang  wrote:

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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.h... where the DotStatements type can have DotSubGraph values, which in turn have DotStatements).

-- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com