Generic.Random.DerivingVia

Pick a constructor with a given distribution, and fill its fields with recursive calls to arbitrary.

Example

data X = ...
  deriving Arbitrary via (GenericArbitrary '[2, 3, 5] X)

Picks the first constructor with probability 2/10, the second with probability 3/10, the third with probability 5/10.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitrary.

Pick every constructor with equal probability.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitraryU.

arbitrary for types with one constructor. Equivalent to GenericArbitraryU, with a stricter type.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitrarySingle.

Decrease size at every recursive call, but don't do anything different at size 0.

data X = ...
  deriving Arbitrary via (GenericArbitraryRec '[2, 3, 5] X)

N.B.: This replaces the generator for fields of type [t] with listOf' arbitrary instead of Test.QuickCheck.listOf arbitrary (i.e., arbitrary for lists).

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitraryRec.

GenericArbitrary with explicit generators.

Example

data X = ...
  deriving Arbitrary via (GenericArbitraryG CustomGens '[2, 3, 5] X)

where, for example, custom generators to override String and Int fields might look as follows:

type CustomGens = CustomString :+ CustomInt

Note on multiple matches

Multiple generators may match a given field: the first will be chosen.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitraryG.

GenericArbitraryU with explicit generators. See also GenericArbitraryG.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitraryUG.

genericArbitrarySingle with explicit generators. See also GenericArbitraryG.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitrarySingleG.

genericArbitraryRec with explicit generators. See also genericArbitraryG.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitraryRecG.

General generic generator with custom options.

This newtype does no shrinking. To add generic shrinking, use AndShrinking.

Uses genericArbitraryWith.

Add generic shrinking to a newtype wrapper for Arbitrary, using genericShrink.

data X = ...
  deriving Arbitrary via (GenericArbitrary '[1,2,3] `AndShrinking' X)

Equivalent to:

instance Arbitrary X where
  arbitrary = genericArbitrary (1 % 2 % 3 % ())
  shrink = genericShrink