Moves Orbit class to separate file. Adds more types of products

ons-hs.cabal

@@ -18,10 +18,13 @@ library
   exposed-modules:     EquivariantMap
                      , EquivariantSet
                      , Orbit
+                     , Orbit.Class
+                     , Orbit.Products
                      , Support
   build-depends:       base >= 4.7 && < 5
                      , containers
                      , data-ordlist
+                     , MemoTrie
   default-language:    Haskell2010
 
 executable ons-hs-exe

src/EquivariantSet.hs

@@ -108,12 +108,12 @@ filter f (EqSet s) = EqSet . Set.filter (f . getElementE) $ s
 -- precondition: f is equivariant
 -- Note that f may change the ordering
 map :: (Orbit a, Orbit b, Ord (Orb b)) => (a -> b) -> EquivariantSet a -> EquivariantSet b
-map f = EqSet . Set.map (toOrbit . f . getElementE) . unEqSet
+map f = EqSet . Set.map (omap f) . unEqSet
 
 -- f should also preserve order on the orbit types!
 -- This means you should know the representation to use it well
 mapMonotonic :: (Orbit a, Orbit b) => (a -> b) -> EquivariantSet a -> EquivariantSet b
-mapMonotonic f = EqSet . Set.mapMonotonic (toOrbit . f . getElementE) . unEqSet
+mapMonotonic f = EqSet . Set.mapMonotonic (omap f) . unEqSet
 
 
 -- Conversion

src/Orbit.hs

@@ -3,39 +3,29 @@
 {-# LANGUAGE StandaloneDeriving #-}
 {-# LANGUAGE TypeFamilies #-}
 
-module Orbit where
+module Orbit
+  ( module Orbit
+  , module Orbit.Class
+  ) where
 
 import Support (Support, Rat(..))
 import qualified Support
 
+import Orbit.Products
+import Orbit.Class
+
 -- TODO: Make generic instances (we already have sums and products)
 -- TODO: For products: replace [Ordering] with Vec Ordering if better
 -- TODO: replace Support by an ordered vector / list for speed?
 
 
--- This is the main meat of the package. The Orbit typeclass, it gives us ways
--- to manipulate nominal elements in sets and maps. The type class has
--- associated data to represent an orbit of type a. This is often much easier
--- than the type a itself. For example, all orbits of Rat are equal.
--- Furthermore, we provide means to go back and forth between elements and
--- orbits, and we get to know their support size. For many manipulations we
--- need an Ord instance on the associated data type, this can often be
--- implemented, even when the type 'a' does not have an Ord instance.
---
--- Laws / conditions:
--- * index . toOrbit == Set.size . support
--- * getElement o s is defined if index o == Set.size s
-class Orbit a where
-  data Orb a :: *
-  toOrbit :: a -> Orb a
-  support :: a -> Support
-  getElement :: Orb a -> Support -> a
-  index :: Orb a -> Int
-
 -- We can get 'default' values, if we don't care about the support.
 getElementE :: Orbit a => Orb a -> a
 getElementE orb = getElement orb (Support.def (index orb))
 
+-- We can `map` orbits to orbits for equivariant functions
+omap :: (Orbit a, Orbit b) => (a -> b) -> Orb a -> Orb b
+omap f = toOrbit . f . getElementE
 
 -- We can construct orbits from rational numbers. There is exactly one orbit,
 -- so this can be represented by the unit type.
@@ -113,8 +103,8 @@ deriving instance (Eq (Orb a), Eq (Orb b)) => Eq (Orb (a, b))
 deriving instance (Ord (Orb a), Ord (Orb b)) => Ord (Orb (a, b))
 
 -- Could be in prelude or some other general purpose lib
-partitionOrd :: (a -> Ordering) -> [a] -> ([a],[a])
+{-# INLINABLE partitionOrd #-}
-{-# INLINE partitionOrd #-}
+partitionOrd :: (a -> Ordering) -> [a] -> ([a], [a])
 partitionOrd p xs = foldr (selectOrd p) ([], []) xs
 
 selectOrd :: (a -> Ordering) -> a -> ([a], [a]) -> ([a], [a])
@@ -123,19 +113,21 @@ selectOrd f x ~(ls, rs) = case f x of
   EQ -> (x : ls, x : rs)
   GT -> (ls, x : rs)
 
--- Enumerate all orbits in a product. In lexicographical order!
+-- Enumerate all orbits in a product A x B. In lexicographical order!
 product :: (Orbit a, Orbit b) => Orb a -> Orb b -> [Orb (a, b)]
 product oa ob = OrbPair oa ob <$> prodStrings (index oa) (index ob)
 
--- I tried Seq [Ordering], it was slower
+-- Separated product: A * B = { (a,b) | Exist C1, C2 disjoint supporting a, b resp.}
-prodStrings :: Int -> Int -> [[Ordering]]
+separatedProduct :: (Orbit a, Orbit b) => Orb a -> Orb b -> [Orb (a, b)]
-prodStrings 0 0 = [[]]
+separatedProduct oa ob = OrbPair oa ob <$> sepProdStrings (index oa) (index ob)
-prodStrings 0 n = [replicate n GT]
+
-prodStrings n 0 = [replicate n LT]
+-- "Left product": A |x B = { (a,b) | C supports a => C supports b }
-prodStrings 1 1 = [[LT, GT], [EQ], [GT, LT]]
+leftProduct :: (Orbit a, Orbit b) => Orb a -> Orb b -> [Orb (a, b)]
-prodStrings n m = ((LT :) <$> prodStrings (n-1) m)
+leftProduct oa ob = OrbPair oa ob <$> rincProdStrings (index oa) (index ob)
-  ++ ((EQ :) <$> prodStrings (n-1) (m-1))
+
-  ++ ((GT :) <$> prodStrings n (m-1))
+{-# INLINABLE product #-}
+{-# INLINABLE separatedProduct #-}
+{-# INLINABLE leftProduct #-}
 
 
 -- Data structure for the discrete nominal sets with a trivial action.

src/Orbit/Class.hs

@@ -0,0 +1,56 @@
+{-# LANGUAGE TypeFamilies #-}
+
+module Orbit.Class where
+
+import Support
+
+-- This is the main meat of the package. The Orbit typeclass, it gives us ways
+-- to manipulate nominal elements in sets and maps. The type class has
+-- associated data to represent an orbit of type a. This is often much easier
+-- than the type a itself. For example, all orbits of Rat are equal.
+-- Furthermore, we provide means to go back and forth between elements and
+-- orbits, and we get to know their support size. For many manipulations we
+-- need an Ord instance on the associated data type, this can often be
+-- implemented, even when the type 'a' does not have an Ord instance.
+--
+-- Laws / conditions:
+-- * index . toOrbit == Set.size . support
+-- * getElement o s is defined if index o == Set.size s
+class Orbit a where
+  data Orb a :: *
+  toOrbit :: a -> Orb a
+  support :: a -> Support
+  getElement :: Orb a -> Support -> a
+  index :: Orb a -> Int
+
+
+{-
+I tried to do generics, but failed. One cannot do generic injective
+data constructors. I will keep it here now, for later reference.
+
+{-# language DefaultSignatures #-}
+{-# LANGUAGE FlexibleContexts #-}
+import GHC.Generic
+
+  default Orb a :: (Generic a, GOrbit (Rep a)) => *
+  data Orb a = Orb () -- how to make a default data instance declaration?
+
+  default toOrbit :: (Generic a, GOrbit (Rep a)) => a -> Orb a
+  toOrbit = _ . gtoOrbit . from
+
+  default support :: (Generic a, GOrbit (Rep a)) => a -> Support
+  support = gsupport . from
+
+  default getElement :: (Generic a, GOrbit (Rep a)) => Orb a -> Support -> a
+  getElement = undefined
+
+  default index :: (Generic a, GOrbit (Rep a)) => Orb a -> Int
+  index = undefined
+
+class GOrbit f where
+  data GOrb f :: * -> *
+  gtoOrbit :: f a -> GOrb f a
+  gsupport :: f a -> Support
+  ggetElement :: GOrb f a -> Support -> f a
+  gindex :: GOrb f a -> Int
+-}

src/Orbit/Products.hs

@@ -0,0 +1,41 @@
+module Orbit.Products where
+
+import Control.Applicative
+import Data.MemoTrie
+
+prodStrings :: Alternative f => Int -> Int -> f [Ordering]
+prodStrings = memo2 gen where
+  gen 0 0 = pure []
+  gen 0 n = pure $ replicate n GT
+  gen n 0 = pure $ replicate n LT
+  gen 1 1 = pure [LT, GT] <|> pure [EQ] <|> pure [GT, LT]
+  gen n m = (LT :) <$> prodStrings (n-1) m
+        <|> (EQ :) <$> prodStrings (n-1) (m-1)
+        <|> (GT :) <$> prodStrings n (m-1)
+
+sepProdStrings :: Alternative f => Int -> Int -> f [Ordering]
+sepProdStrings = memo2 gen where
+  gen 0 0 = pure []
+  gen 0 n = pure $ replicate n GT
+  gen n 0 = pure $ replicate n LT
+  gen 1 1 = pure [LT, GT] <|> pure [GT, LT]
+  gen n m = (LT :) <$> sepProdStrings (n-1) m
+        <|> (GT :) <$> sepProdStrings n (m-1)
+
+rincProdStrings :: Alternative f => Int -> Int -> f [Ordering]
+rincProdStrings = memo2 gen where
+  gen n 0 = pure $ replicate n LT
+  gen 0 _ = empty
+  gen 1 1 = pure [EQ]
+  gen n m 
+    | n < m     = empty
+    | otherwise = (LT :) <$> rincProdStrings (n-1) m
+              <|> (EQ :) <$> rincProdStrings (n-1) (m-1)
+
+{-# INLINABLE prodStrings #-}
+{-# INLINABLE sepProdStrings #-}
+{-# INLINABLE rincProdStrings #-}
+
+{-# SPECIALIZE prodStrings :: Int -> Int -> [[Ordering]] #-}
+{-# SPECIALIZE sepProdStrings :: Int -> Int -> [[Ordering]] #-}
+{-# SPECIALIZE rincProdStrings :: Int -> Int -> [[Ordering]] #-}

stack.yaml

@@ -15,7 +15,7 @@
 # resolver:
 #  name: custom-snapshot
 #  location: "./custom-snapshot.yaml"
-resolver: lts-9.10
+resolver: lts-10.5
 
 # User packages to be built.
 # Various formats can be used as shown in the example below.