0.1.0.1

CHANGELOG.md

@@ -3,3 +3,7 @@
 ## 0.1.0.0 -- 2020-02-18
 
 * Initial release.
+
+## 0.1.0.1 -- 2020-02-19
+
+* Add `ToTuple`, `FromTuple` and `uncons`.

indexed-containers.cabal

@@ -4,7 +4,7 @@ cabal-version:       2.4
 -- http://haskell.org/cabal/users-guide/
 
 name:                indexed-containers
-version:             0.1.0.0
+version:             0.1.0.1
 synopsis:            Simple, no-frills indexed lists.
 description:         If the lengths of your lists are known statically, using indexed lists improves type safety with no runtime overhead.
 category:            Data Structures

src/Data/NList.hs

@@ -1,6 +1,7 @@
 {-# LANGUAGE AllowAmbiguousTypes #-}
 {-# LANGUAGE CPP #-}
 {-# LANGUAGE DataKinds #-}
+{-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE TypeOperators #-}
@@ -10,6 +11,8 @@
 {-# LANGUAGE NoStarIsType #-}
 #endif
 
+{-# OPTIONS_GHC -fno-warn-incomplete-patterns #-}
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.NList
@@ -40,6 +43,7 @@ module Data.NList
   , init
   , init'
   , initMay
+  , uncons
   , toList
 
   -- * Extracing sublists
@@ -81,6 +85,10 @@ module Data.NList
   , mk9
   , mk10
 
+  -- * To and from tuples
+  , FromTuple(..)
+  , ToTuple(..)
+
   -- * Predecessor of a Nat
   , Pred
   ) where
@@ -210,6 +218,13 @@ initMay :: NList n a -> Maybe (NList (Pred n) a)
 initMay (List []) = Nothing
 initMay (List xs) = Just $ List (List.init xs)
 
+-- | Decompose a list into head and tail.
+--
+-- > uncons (singleton 'a') === ('a', empty)
+-- > uncons (mk3 'a' 'b' 'c') === ('a', mk2 'b' 'c')
+uncons :: (1 <= n) => NList n a -> (a, NList (n-1) a)
+uncons (List (x:xs)) = (x, List xs)
+
 -- | Return the first @k@ elements of a list whose length is at least @k@.
 --
 -- > take @0 (mk3 'a' 'b' 'c') === empty
@@ -378,6 +393,108 @@ mk9 a1 a2 a3 a4 a5 a6 a7 a8 a9 = List [a1, a2, a3, a4, a5, a6, a7, a8, a9]
 mk10 :: a -> a -> a -> a -> a -> a -> a -> a -> a -> a -> NList 10 a
 mk10 a1 a2 a3 a4 a5 a6 a7 a8 a9 a10 = List [a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]
 
+
+-- | Typeclass for converting tuples to 'NList's.
+class FromTuple a where
+  type List a
+  fromTuple :: a -> List a
+
+instance FromTuple (a, a) where
+  type List (a, a) = NList 2 a
+  -- > fromTuple ('a', 'b') === mk2 'a' 'b'
+  fromTuple (a1, a2) = mk2 a1 a2
+
+instance FromTuple (a, a, a) where
+  type List (a, a, a) = NList 3 a
+  -- > fromTuple ('a', 'b', 'c') === mk3 'a' 'b' 'c'
+  fromTuple (a1, a2, a3) = mk3 a1 a2 a3
+
+instance FromTuple (a, a, a, a) where
+  type List (a, a, a, a) = NList 4 a
+  -- > fromTuple ('a', 'b', 'c', 'd') === mk4 'a' 'b' 'c' 'd'
+  fromTuple (a1, a2, a3, a4) = mk4 a1 a2 a3 a4
+
+instance FromTuple (a, a, a, a, a) where
+  type List (a, a, a, a, a) = NList 5 a
+  -- > fromTuple ('a', 'b', 'c', 'd', 'e') === mk5 'a' 'b' 'c' 'd' 'e'
+  fromTuple (a1, a2, a3, a4, a5) = mk5 a1 a2 a3 a4 a5
+
+instance FromTuple (a, a, a, a, a, a) where
+  type List (a, a, a, a, a, a) = NList 6 a
+  -- > fromTuple ('a', 'b', 'c', 'd', 'e', 'f') === mk6 'a' 'b' 'c' 'd' 'e' 'f'
+  fromTuple (a1, a2, a3, a4, a5, a6) = mk6 a1 a2 a3 a4 a5 a6
+
+instance FromTuple (a, a, a, a, a, a, a) where
+  type List (a, a, a, a, a, a, a) = NList 7 a
+  -- > fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g') === mk7 'a' 'b' 'c' 'd' 'e' 'f' 'g'
+  fromTuple (a1, a2, a3, a4, a5, a6, a7) = mk7 a1 a2 a3 a4 a5 a6 a7
+
+instance FromTuple (a, a, a, a, a, a, a, a) where
+  type List (a, a, a, a, a, a, a, a) = NList 8 a
+  -- > fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h') === mk8 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h'
+  fromTuple (a1, a2, a3, a4, a5, a6, a7, a8) = mk8 a1 a2 a3 a4 a5 a6 a7 a8
+
+instance FromTuple (a, a, a, a, a, a, a, a, a) where
+  type List (a, a, a, a, a, a, a, a, a) = NList 9 a
+  -- > fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i') === mk9 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i'
+  fromTuple (a1, a2, a3, a4, a5, a6, a7, a8, a9) = mk9 a1 a2 a3 a4 a5 a6 a7 a8 a9
+
+instance FromTuple (a, a, a, a, a, a, a, a, a, a) where
+  type List (a, a, a, a, a, a, a, a, a, a) = NList 10 a
+  -- > fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j') === mk10 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j'
+  fromTuple (a1, a2, a3, a4, a5, a6, a7, a8, a9, a10) = mk10 a1 a2 a3 a4 a5 a6 a7 a8 a9 a10
+
+
+-- | Typeclass for converting 'NList's to tuples.
+class ToTuple a where
+  type Tuple a
+  toTuple :: a -> Tuple a
+
+instance ToTuple (NList 2 a) where
+  type Tuple (NList 2 a) = (a, a)
+  -- > toTuple (mk2 'a' 'b') === ('a', 'b')
+  toTuple (List [a1, a2]) = (a1, a2)
+
+instance ToTuple (NList 3 a) where
+  type Tuple (NList 3 a) = (a, a, a)
+  -- > toTuple (mk3 'a' 'b' 'c') === ('a', 'b', 'c')
+  toTuple (List [a1, a2, a3]) = (a1, a2, a3)
+
+instance ToTuple (NList 4 a) where
+  type Tuple (NList 4 a) = (a, a, a, a)
+  -- > toTuple (mk4 'a' 'b' 'c' 'd') === ('a', 'b', 'c', 'd')
+  toTuple (List [a1, a2, a3, a4]) = (a1, a2, a3, a4)
+
+instance ToTuple (NList 5 a) where
+  type Tuple (NList 5 a) = (a, a, a, a, a)
+  -- > toTuple (mk5 'a' 'b' 'c' 'd' 'e') === ('a', 'b', 'c', 'd', 'e')
+  toTuple (List [a1, a2, a3, a4, a5]) = (a1, a2, a3, a4, a5)
+
+instance ToTuple (NList 6 a) where
+  type Tuple (NList 6 a) = (a, a, a, a, a, a)
+  -- > toTuple (mk6 'a' 'b' 'c' 'd' 'e' 'f') === ('a', 'b', 'c', 'd', 'e', 'f')
+  toTuple (List [a1, a2, a3, a4, a5, a6]) = (a1, a2, a3, a4, a5, a6)
+
+instance ToTuple (NList 7 a) where
+  type Tuple (NList 7 a) = (a, a, a, a, a, a, a)
+  -- > toTuple (mk7 'a' 'b' 'c' 'd' 'e' 'f' 'g') === ('a', 'b', 'c', 'd', 'e', 'f', 'g')
+  toTuple (List [a1, a2, a3, a4, a5, a6, a7]) = (a1, a2, a3, a4, a5, a6, a7)
+
+instance ToTuple (NList 8 a) where
+  type Tuple (NList 8 a) = (a, a, a, a, a, a, a, a)
+  -- > toTuple (mk8 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h') === ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h')
+  toTuple (List [a1, a2, a3, a4, a5, a6, a7, a8]) = (a1, a2, a3, a4, a5, a6, a7, a8)
+
+instance ToTuple (NList 9 a) where
+  type Tuple (NList 9 a) = (a, a, a, a, a, a, a, a, a)
+  -- > toTuple (mk9 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i') === ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i')
+  toTuple (List [a1, a2, a3, a4, a5, a6, a7, a8, a9]) = (a1, a2, a3, a4, a5, a6, a7, a8, a9)
+
+instance ToTuple (NList 10 a) where
+  type Tuple (NList 10 a) = (a, a, a, a, a, a, a, a, a, a)
+  -- > toTuple (mk10 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j') === ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j')
+  toTuple (List [a1, a2, a3, a4, a5, a6, a7, a8, a9, a10]) = (a1, a2, a3, a4, a5, a6, a7, a8, a9, a10)
+
 instance (KnownNat n, Show a) => Show (NList n a) where
   showsPrec p (List xs) = showParen (p > 10) $
     showString "List " . shows (natVal (Proxy :: Proxy n)) . showString " " . shows xs

test/hspec/Data/NListSpec.hs

@@ -45,6 +45,8 @@ spec = do
       initMay (empty :: NList 0 ()) === Nothing
       initMay (singleton 'a') === Just empty
       initMay (mk3 'a' 'b' 'c') === Just (mk2 'a' 'b')
+      uncons (singleton 'a') === ('a', empty)
+      uncons (mk3 'a' 'b' 'c') === ('a', mk2 'b' 'c')
       take @0 (mk3 'a' 'b' 'c') === empty
       take @2 (mk3 'a' 'b' 'c') === mk2 'a' 'b'
       take @3 (mk3 'a' 'b' 'c') === mk3 'a' 'b' 'c'
@@ -80,3 +82,21 @@ spec = do
       toList (mk8 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h') === "abcdefgh"
       toList (mk9 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i') === "abcdefghi"
       toList (mk10 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j') === "abcdefghij"
+      fromTuple ('a', 'b') === mk2 'a' 'b'
+      fromTuple ('a', 'b', 'c') === mk3 'a' 'b' 'c'
+      fromTuple ('a', 'b', 'c', 'd') === mk4 'a' 'b' 'c' 'd'
+      fromTuple ('a', 'b', 'c', 'd', 'e') === mk5 'a' 'b' 'c' 'd' 'e'
+      fromTuple ('a', 'b', 'c', 'd', 'e', 'f') === mk6 'a' 'b' 'c' 'd' 'e' 'f'
+      fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g') === mk7 'a' 'b' 'c' 'd' 'e' 'f' 'g'
+      fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h') === mk8 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h'
+      fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i') === mk9 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i'
+      fromTuple ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j') === mk10 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j'
+      toTuple (mk2 'a' 'b') === ('a', 'b')
+      toTuple (mk3 'a' 'b' 'c') === ('a', 'b', 'c')
+      toTuple (mk4 'a' 'b' 'c' 'd') === ('a', 'b', 'c', 'd')
+      toTuple (mk5 'a' 'b' 'c' 'd' 'e') === ('a', 'b', 'c', 'd', 'e')
+      toTuple (mk6 'a' 'b' 'c' 'd' 'e' 'f') === ('a', 'b', 'c', 'd', 'e', 'f')
+      toTuple (mk7 'a' 'b' 'c' 'd' 'e' 'f' 'g') === ('a', 'b', 'c', 'd', 'e', 'f', 'g')
+      toTuple (mk8 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h') === ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h')
+      toTuple (mk9 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i') === ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i')
+      toTuple (mk10 'a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j') === ('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j')