CODEWITHSUNDEEP
haskellfunctional-programminggeneratorquickcheck
dfj328
dfj328

Reputation: 367

Creating generators from user defined data types in haskell

I need some suggestions on how I can go about creating a random generator for the Foo data type such that the list of Boo is never empty?

data Boo = Boo Float Float Float
data Foo = Foo Float Float Float [Boo]

Upvotes: 2

Views: 103

Answers (1)

Frerich Raabe
Frerich Raabe

Reputation: 94439

You can use the listOf1 function to get a generator which generates non-empty lists and use that for defining an appropriate Arbitrary instance, like:

import Test.QuickCheck
import Control.Applicative

instance Arbitrary Boo

instance Arbitrary Foo where
  arbitrary = Foo <$> arbitrary <*> arbitrary <*> arbitrary <*> listOf1 arbitrary

Upvotes: 7

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