validated-types-0.1.1: src/Refined/Length.hs

{-# LANGUAGE MultiParamTypeClasses #-}
{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE DataKinds #-}
{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE RankNTypes #-}
{-# LANGUAGE ScopedTypeVariables #-}
module Refined.Length where

import Refined (Predicate(..))
import Refined (EqualTo)
import Refined.LessThanEq (LessThanEq)
import Data.CharLength (CharLength(..))

import GHC.TypeLits (Nat)


-- | The length of an input
data Length p

instance (CharLength x, Predicate p Int) => Predicate (Length p) x where
  validate _ x =
    showString "Length of string: " <$>
      validate (undefined :: p) (charLength x)


type LengthEq (n :: Nat) =
    Length (EqualTo n)

type LengthMax (n :: Nat) =
    Length (LessThanEq n)