Safe Haskell	None
Language	GHC2021

Effectful.Dynamic.Utils

Description

Since: 0.1

Synopsis

class ShowEffect (p :: (Type -> Type) -> Type -> Type) where
- showEffectCons :: forall (m :: Type -> Type) a. p m a -> String

Documentation

class ShowEffect (p :: (Type -> Type) -> Type -> Type) where Source #

Class for "showing" a dynamic effect. This class is intended for debugging or error handling.

Methods

showEffectCons :: forall (m :: Type -> Type) a. p m a -> String Source #

Shows an effect constructor. Useful for stubbing mock effects e.g.

  runEffect = interpret_ $ case
    Cons1 x -> ...
    Cons2 x y -> ...
    other -> error $ (showEffectCons other) ++ ": unimplemented"

We may not want to provide an implementation for all members of a mock effect e.g. because we want to verify a specific member is _not_ used, or implementing everything is unnecessarily cumbersome.

Erroring out is a reasonable choice, though it can lead to cryptic errors if such a member _is_ (unexpectedly) used and subsequently fails. Thus this show instance can be used to provide a better error message.