Module

Error.Control

Package: purescript-errorcontrol
Repository: purescript/purescript-prelude

#ErrorControl Source

class (MonadThrow e f, Monad g) <= ErrorControl f g e | f -> e, f -> g where

A type class for principled Error handling. ErrorControl allows to represent already handled errors in the type system by switching to an unexceptional type constructor g. Find more here: https://lukajcb.github.io/blog/functional/2018/04/15/rethinking-monaderror.html

Should respect the following laws:

Catch: controlError (throwError e) f === f e
Pure: controlError (pure a) f === pure a
No Errors in g: handleBlunder (accept ga) f === ga

Members

controlError :: forall a. f a -> (e -> g a) -> g a
accept :: g ~> f

Instances

ErrorControl (Either e) Identity e
(Monad f) => ErrorControl (ExceptT e f) f e
(ErrorControl f g e) => ErrorControl (StateT s f) (StateT s g) e

#intercept Source

intercept :: forall a e g f. ErrorControl f g e => f a -> (e -> a) -> g a

#trial Source

trial :: forall a e g f. ErrorControl f g e => Monad f => f a -> g (Either e a)

#absolve Source

absolve :: forall a e g f. ErrorControl f g e => Monad f => g (Either e a) -> f a

#assure Source

assure :: forall a e g f. ErrorControl f g e => Monad f => g a -> (a -> e) -> (a -> Boolean) -> f a

Modules: Error.Control