Data.Unfoldable.Trivial.Internal

newtype Trivial a

A type wrapping unfoldr calls, existentially quantified over the seed type so that it can be ignored in the type constructor. Its Unfoldable instance means that it can directly be constructed by calling unfoldr.

Instances

• Unfoldable Trivial

  Wraps both arguments to unfoldr in an UnfoldrCall.

• Unfoldable1 Trivial
• Functor Trivial
• Invariant Trivial
• Foldable Trivial

  The raison d'être for Trivial. Allows folding polymorphic Unfoldables as they generate.

  foldr uses a default implementation and may be inefficient. Note also that this enables the use of sequence_ despite the lack of a Traversable instance, which is not provided because it would require forcing and accumulating every value, at which point any would-be user is better off with an actual container.

• (Arbitrary a, Coarbitrary a) => Arbitrary (Trivial a)

  Guaranteed finite.

• Lazy (Trivial a)
• Compactable Trivial
• Filterable Trivial
• Semigroup (Trivial a)

  Concatenation.

  Do not use this to create a data structure. Please use Data.List.Lazy instead.

• Plus Trivial
• Alt Trivial

  Not concatenation! (<|>) clobbers a prefix of the right argument of the length of the left in order to satisfy the Alternative laws. (Thanks to @xgrommx's implementation in ZipList!)

• Monoid (Trivial a)
• Apply Trivial

  Zipwith; chosen over the Monad-compatible nondet choice used for Array etc. because that would require effectively forcing one argument and either re-evaluating it constantly or storing its elements in a real container at which point please please please just do that without using Trivial. Length is the minimum of the arguments' lengths.

• Applicative Trivial

  Infinitely cycles to satisfy the Applicative laws! If you just want one element, use singleton instead.

• Alternative Trivial
• (Eq a) => Eq (Trivial a)

  Does not and cannot memoize the values being produced to compare. Please consider using Data.List.Lazy or your strict container of choice instead if you have any intention of using this for anything else.

• (Ord a) => Ord (Trivial a)
• Eq1 Trivial
• Ord1 Trivial
• (Show a) => Show (Trivial a)

type Generator a b = b -> Maybe (a /\ b)

Alias for the generator function passed to unfoldr.

trivial :: forall a. Trivial a -> Trivial a

Specializes its argument to Trivial.

untrivial :: forall a c. (forall b. Generator a b -> b -> c) -> Trivial a -> c

Convenience function for inspecting Trivial values. Calls the function argument on the contents of the inner Exists.

turbofish :: forall a b. (Trivial a -> b) -> Trivial a -> b

Function application specialized to a Trivial argument, at the same precedence as ($).

Inspired by the Rust syntax of the same name, often used in the analogous context of collecting from an iterator.

Operator alias for Data.Unfoldable.Trivial.Internal.turbofish (right-associative / precedence 0)

unfoldr1Default :: forall a b t. Unfoldable t => (b -> a /\ (Maybe b)) -> b -> t a

Provides a default implementation of unfoldr1 using unfoldr to satisfy the superclass bound on Unfoldable.

runTrivial :: forall a u. Unfoldable u => Trivial a -> u a

Converts to any other Unfoldable. Can also be seen as evaluating the inner UnfoldrCall.

This is only useful in implementing utility functions. In all other cases, simply use the desired type directly.