testing-feat- Functional Enumeration of Algebraic Types

Safe HaskellNone




Everything you need to construct an enumeration for an algebraic type. Just define each constructor using pure for nullary constructors and unary and funcurry for positive arity constructors, then combine the constructors with consts. Example:

  instance Enumerable a => Enumerable [a] where
    enumerate = consts [unary (funcurry (:)), pure []]

There's also a handy Template Haskell function for automatic derivation.



class Typeable a => Enumerable a whereSource

A class of functionally enumerable types


enumerate :: Enumerate aSource

This is the interface for defining an instance. When combining enumerations use shared instead and when accessing the data of enumerations use optimal.


Enumerable Bool 
Enumerable Char

Contains only ASCII characters

Enumerable Double

Not injective

Enumerable Float

Not injective

Enumerable Int 
Enumerable Int8 
Enumerable Int16 
Enumerable Int32 
Enumerable Int64 
Enumerable Integer 
Enumerable Ordering 
Enumerable Word 
Enumerable Word8 
Enumerable Word16 
Enumerable Word32 
Enumerable Word64 
Enumerable () 
Enumerable Printable 
Enumerable Unicode 
Enumerable a_12 => Enumerable [a_12] 
(Infinite a, Enumerable a) => Enumerable (Ratio a)

Not injective

Enumerable a_a1aW => Enumerable (Maybe a_a1aW) 
(Infinite a, Enumerable a) => Enumerable (NonZero a) 
Infinite a => Enumerable (Nat a) 
Enumerable a => Enumerable (NonEmpty a) 
(Enumerable a_acKx, Enumerable b_acKy) => Enumerable (Either a_acKx b_acKy) 
(Enumerable a_12, Enumerable b_13) => Enumerable (a_12, b_13) 
(Enumerable a, Enumerable b) => Enumerable (FreePair a b) 
(Enumerable a_12, Enumerable b_13, Enumerable c_14) => Enumerable (a_12, b_13, c_14) 
(Enumerable a_12, Enumerable b_13, Enumerable c_14, Enumerable d_15) => Enumerable (a_12, b_13, c_14, d_15) 
(Enumerable a_12, Enumerable b_13, Enumerable c_14, Enumerable d_15, Enumerable e_16) => Enumerable (a_12, b_13, c_14, d_15, e_16) 
(Enumerable a_12, Enumerable b_13, Enumerable c_14, Enumerable d_15, Enumerable e_16, Enumerable f_17) => Enumerable (a_12, b_13, c_14, d_15, e_16, f_17) 
(Enumerable a_12, Enumerable b_13, Enumerable c_14, Enumerable d_15, Enumerable e_16, Enumerable f_17, Enumerable g_18) => Enumerable (a_12, b_13, c_14, d_15, e_16, f_17, g_18) 

Building instances

nullary :: a -> Constructor aSource

For nullary constructors such as True and [].

unary :: Enumerable a => (a -> b) -> Constructor bSource

For any non-nullary constructor. Apply funcurry until the type of the result is unary (i.e. n-1 times where n is the number of fields of the constructor).

funcurry :: (a -> b -> c) -> FreePair a b -> cSource

Uncurry a function (typically a constructor) to a function on free pairs.

consts :: [Constructor a] -> Enumerate aSource

Produces the enumeration of a type given the enumerators for each of its constructors. The result of unary should typically not be used directly in an instance even if it only has one constructor. So you should apply consts even in that case.

Accessing the enumerator of an instance

shared :: Enumerable a => Enumerate aSource

Version of enumerate that ensures that the enumeration is shared between all accesses. Should always be used when combining enumerations.

optimal :: Enumerable a => Enumerate aSource

An optimal version of enumerate. Used by all library functions that access enumerated values (but not by combining functions). Library functions should ensure that optimal is not reevaluated.

Free pairs

newtype FreePair a b Source

A free pair constructor. The cost of constructing a free pair is equal to the sum of the costs of its components.




free :: (a, b)


Deriving instances with template Haskell

deriveEnumerable :: Name -> Q [Dec]Source

Derive an instance of Enumberable with Template Haskell. To derive an instance for Enumerable A, just put this as a top level declaration in your module (with the TemplateHaskell extension enabled):

   deriveEnumerable ''A

deriveEnumerable' :: ConstructorDeriv -> Q [Dec]Source

Derive an instance of Enumberable with Template Haskell, with rules for some specific constructors