type-fun-0.1.2: example/Main.hs

module Main where

import Data.Proxy
import TypeFun.Data.List
import TypeFun.Data.Peano

-- | This function has wider constraint __Int is inside l__
elemConstr :: (Elem Int l) => proxy l -> Int
elemConstr p = 1

-- | This function has narrower constraint than 'elemConstr'
-- __Int and Bool are contained in l__
sublistConstr :: (SubList '[Int, Bool] l) => proxy l -> Int
sublistConstr p = elemConstr p + 1

-- | This function has narrower constraint than 'sublistConstr' (Order
-- of elements matters)
prefixConstr :: (IsPrefixOf '[Int, Bool] l) => proxy l -> Int
prefixConstr p = sublistConstr p + 1

-- | This function has narrower constraint
-- __Int is inside of l and it is a first argument__
-- and uses inside more wide function
indexConstr :: (('Just 'Z) ~ (IndexOfMay Int l)) => proxy l -> Int
indexConstr p = elemConstr p + 1

uniqConstr :: (UniqElements l) => proxy l -> Int
uniqConstr _ = 1

main :: IO ()
main = do
  let
    p2 = Proxy :: Proxy '[Int, Bool]
    p3 = Proxy :: Proxy '[Int, Bool, Int]
  print $ indexConstr p2
  print $ sublistConstr p2
  print $ prefixConstr p2
  print $ prefixConstr p3
  print $ uniqConstr p2
  print $ peanoVal (Proxy :: Proxy (FromNat 100))
  -- print $ uniqConstr p3 -- < ElementIsNotUniqInList Int '[Int, Bool, Int]