Lift.hs

{-|

@
(lift CapitalLetterA :: Word8) == 65

(lift [CapitalLetterH, SmallLetterI, ExclamationMark] :: Text) == "Hi!"
@ -}
module ASCII.Lift (Lift (..)) where

import ASCII.Case (Case (..))
import ASCII.CaseRefinement (ASCII'case)
import ASCII.Char (Char)
import ASCII.Refinement (ASCII)
import ASCII.Superset (CharSuperset, StringSuperset)

import qualified ASCII.CaseRefinement as CaseRefinement
import qualified ASCII.Refinement as Refinement
import qualified ASCII.Superset as S

import qualified Prelude

import Data.Function ((.))

{-| Embedding of one character set within another

The @subset@ and @superset@ types may be characters or strings in
ASCII, some subset of ASCII, or some superset of ASCII. -}
class Lift subset superset where

    {-| Converts from a smaller to a larger type

    Due to the highly polymorphic nature of the 'lift' function,
    often it must used with an explicit type signature or type
    application to avoid any type ambiguity. -}

    lift :: subset -> superset

instance Lift a a where lift x = x

{-| A value from an ASCII superset that has been refined by the 'ASCII' type
constructor may be lifted back into the superset by unwrapping it from the
'ASCII' type. -}
instance Lift (ASCII superset) superset where lift = Refinement.lift

instance Lift (ASCII'case letterCase superset) superset where lift = CaseRefinement.lift

{-| An ASCII 'Char' may be 'lift'ed into any larger character set (a
'CharSuperset'); for example, 'lift' can convert an ASCII character into a value
of the standard 'Prelude.Char' type in "Prelude". -}
instance CharSuperset superset => Lift Char superset where lift = S.fromChar

{-| An ASCII 'Char' list may be 'lift'ed into a string of any larger character
set (a 'StringSuperset'); for example, 'lift' can convert a list of ASCII
characters into a value of the standard 'Prelude.String' type in "Prelude". -}
instance StringSuperset superset => Lift [Char] superset where lift = S.fromCharList