Coerce.hs

{-# LANGUAGE NoImplicitPrelude #-}

{-|
Module      : Headroom.Data.Coerce
Description : Extra functionality for coercion
Copyright   : (c) 2019-2021 Vaclav Svejcar
License     : BSD-3-Clause
Maintainer  : vaclav.svejcar@gmail.com
Stability   : experimental
Portability : POSIX

This module provides some extra functionality extending the "Data.Coerce"
module.
-}

module Headroom.Data.Coerce
  ( coerce
  , inner
  )
where

import           Data.Coerce                         ( Coercible
                                                     , coerce
                                                     )
import           RIO


-- | Allows to map the coercible value. This might be useful for example to
-- change the value within @newtype@, without manually unwrapping and wrapping
-- the value.
--
-- >>> import qualified RIO.Text as T
-- >>> newtype Foo = Foo Text deriving (Eq, Show)
-- >>> inner T.toUpper (Foo "hello")
-- Foo "HELLO"
inner :: (Coercible a b)
      => (b -> b)
      -- ^ function to modify coerced value
      -> a
      -- ^ value to modify
      -> a
      -- ^ modified value
inner f = coerce . f . coerce