This library provides definitions for CEPs (classy-effects protocols) to standardize and unify the definition of effects in Haskell in a backend-library-agnostic manner. Please refer to CEPs for details. This library provides only the fundamental definitions for classy-effects. Please also refer to the classy-effects package, which offers standard effect definitions compliant with CEPs, and the classy-effects-th package, which enables automatic compliance with CEPs. This 'classy-effects' project was abandoned due to the discovery of fundamental difficulties. The reasons are as follows: https://github.com/orgs/sayo-hs/projects/4?pane=issue&itemId=48547880 As an alternative, consider using 'sayo-hs/data-effects', a GADTs-based common effect representation foundation: https://github.com/sayo-hs/data-effects.