Data.FailableList

A list-like type for lazy streams, which might terminate with an error.

This module uses common names and so is designed to be imported qualified:

 import qualified Data.FailableList as FL

Documentation

data FailableList e a

A list-like type for lazy sequences which might terminate with an error.

Standard lists can be converted to failable lists using Prelude.foldr Next Done.

Constructors

Next a (FailableList e a)

Done

Fail e

Instances

Monad (FailableList e)

Functor (FailableList e)

MonadFix (FailableList e)

MonadPlus (FailableList e)

Applicative (FailableList e)

Foldable (FailableList e)

Traversable (FailableList e)

Alternative (FailableList e)

(Eq e, Eq a) => Eq (FailableList e a)

(Show e, Show a) => Show (FailableList e a)

Monoid (FailableList e a)

map :: (a -> Either e b) -> FailableList e a -> FailableList e b

Like the standard map function, but the mapping function may return an error.

foldr :: (a -> b -> b) -> b -> (e -> b) -> FailableList e a -> b

Like the standard foldr function, but accepting an extra parameter to handle Fail items.

unfoldr :: (b -> Either e (Maybe (a, b))) -> b -> FailableList e a

Like the standard Data.List.unfoldr function, but the step function may return an error.