module_example.hs

{-# LANGUAGE ConstraintKinds #-}
{-# LANGUAGE ImplicitParams #-}

{- declaration -}

data MyModuleType =
    MkMyModule
    { mod_global1 :: Int
    , mod_global2 :: String
    }

-- ConstraintKinds lets us write an alias
-- for the implicit param:
type MyModule = (?myModule :: MyModuleType)

-- accessors for 'global' values:

global1 :: MyModule => Int
global1 = mod_global1 ?myModule

global2 :: MyModule => String
global2 = mod_global2 ?myModule

{- usage -}

main =
    -- instantiate module
    let ?myModule = MkMyModule 123 "456" in
    print whatever

-- function that uses module implicitly 
whatever :: MyModule => String
whatever = show global1 ++ global2