Orphans

module Orphans where

data Tuple a b = Tuple a b
    deriving (Eq, Show)

--

{-# LANGUAGE FlexibleInstances #-}

module OrphansFoo where

import Data.Monoid
import Data.Set (Set)
import qualified Data.Set as S

import Orphans

data Foo = Foo1 | Foo2
    deriving (Eq, Ord, Show)

instance Ord b => Ord (Tuple Foo b) where
    compare (Tuple a1 a2) (Tuple b1 b2) = compare a1 b1 <> compare a2 b2

foo :: Ord b => b -> b -> Set (Tuple Foo b)
foo a b = S.fromList [Tuple Foo1 a, Tuple Foo1 b, Tuple Foo2 a, Tuple Foo2 b]

--

{-# LANGUAGE FlexibleInstances #-}

module OrphansBar where

import Data.Monoid
import Data.Set (Set)
import qualified Data.Set as S

import Orphans

data Bar = Bar1 | Bar2
    deriving (Eq, Ord, Show)

instance Ord a => Ord (Tuple a Bar) where
    compare (Tuple a1 a2) (Tuple b1 b2) = compare a2 b2 <> compare a1 b1

bar :: Ord a => a -> a -> Set (Tuple a Bar) -> Set (Tuple a Bar)
bar a b s = S.fromList [Tuple a Bar1, Tuple a Bar2, Tuple b Bar1, Tuple b Bar2] <> s

--

module OrphansBaz where

import Data.Set (Set)

import Orphans
import OrphansFoo
import OrphansBar

baz :: Set (Tuple Foo Bar)
baz = bar Foo1 Foo2 $ foo Bar1 Bar2
-- fromList [Tuple Foo1 Bar1,Tuple Foo2 Bar1,Tuple Foo1 Bar2,Tuple Foo2 Bar1,Tuple Foo1 Bar2,Tuple Foo2 Bar2]