monomorphic (empty) → 0.0.1.0

raw patch · 5 files changed

+160/−0 lines, 5 filesdep +basedep +transformerssetup-changed

Dependencies added: base, transformers

Files

• Data/Type/Monomorphic.hs +57/−0
• LICENSE +30/−0
• README.md +46/−0
• Setup.hs +2/−0
• monomorphic.cabal +25/−0

@@ -0,0 +1,57 @@+{-# LANGUAGE DataKinds, ExistentialQuantification, FlexibleContexts, GADTs #-}+{-# LANGUAGE PolyKinds, RankNTypes, TypeFamilies, TypeOperators            #-}+{-# LANGUAGE UndecidableInstances                                          #-}+module Data.Type.Monomorphic ( (:.:), Monomorphic (..), Monomorphicable(..)+                             , demote', demoteComposed, monomorphicCompose+                             , withPolymorhic, liftPoly, viaPoly, Compose(..)+                             ) where+import Control.Arrow+import Data.Functor.Compose++type (:.:) f g = Compose f g++-- | A wrapper type for polymophic types.+data Monomorphic k = forall a. Monomorphic (k a)++-- | A types which have the monomorphic representation.+class Monomorphicable k where+  -- | Monomorphic representation+  type MonomorphicRep k :: *+  -- | Promote the monomorphic value to the polymophic one.+  promote :: MonomorphicRep k -> Monomorphic k+  -- | Demote the polymorphic value to the monomorphic representation.+  demote  :: Monomorphic k -> MonomorphicRep k++-- | Convinience function to demote polymorphic types into monomorphic one directly.+demote' :: Monomorphicable k => k a -> MonomorphicRep k+demote' = demote . Monomorphic++-- | Demote polymorphic nested types directly into monomorphic representation.+demoteComposed :: Monomorphicable (f :.: g) => f (g a) -> MonomorphicRep (f :.: g)+demoteComposed = demote . Monomorphic . Compose++monomorphicCompose :: f (g a) -> Monomorphic (f :.: g)+monomorphicCompose = Monomorphic . Compose++-- | Apply dependently-typed function to the monomorphic representation.+withPolymorhic :: Monomorphicable k+               => MonomorphicRep k -> (forall a. k a -> b) -> b+withPolymorhic k trans =+  case promote k of+    Monomorphic a -> trans a++-- | Flipped version of 'withPolymorhic'.+liftPoly :: Monomorphicable k+         => (forall a. k a -> b) -> MonomorphicRep k -> b+liftPoly = flip withPolymorhic++-- | Demote the function between polymorphic types into the one between monomorphic one.+viaPoly :: (Monomorphicable k, Monomorphicable k')+        => (forall x y. k x -> k' y) -> MonomorphicRep k -> MonomorphicRep k'+viaPoly f a = demote $ Monomorphic $ liftPoly f a++instance (Show (MonomorphicRep k), Monomorphicable k) => Show (Monomorphic k) where+  showsPrec d x = showString "Polymorphic " . showsPrec (d + 1) (demote x)++instance (Read (MonomorphicRep k), Monomorphicable k) => Read (Monomorphic k) where+  readsPrec i = map (first promote) . readsPrec i

@@ -0,0 +1,30 @@+Copyright (c) 2013, Hiromi ISHII++All rights reserved.++Redistribution and use in source and binary forms, with or without+modification, are permitted provided that the following conditions are met:++    * Redistributions of source code must retain the above copyright+      notice, this list of conditions and the following disclaimer.++    * Redistributions in binary form must reproduce the above+      copyright notice, this list of conditions and the following+      disclaimer in the documentation and/or other materials provided+      with the distribution.++    * Neither the name of Hiromi ISHII nor the names of other+      contributors may be used to endorse or promote products derived+      from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

@@ -0,0 +1,46 @@+The `monomorphic` library+==========================++What is this?+-------------+This library provides the type-class and functions to convert polymorphic data-types to/from its monomorphic representation types.+It is convenient to provide a monomorphic interface for dependently-typed programs.++Usage+-----+Consider the following example:++```haskell+data Nat = Z | S Nat+data SNat (n :: Nat) where+  SZ :: SNat Z+  SS :: SNat n -> SNat (S n)++instance Monomorphicable SNat where+  type MonomorphicRep SNat = Int+  promote 0     = Monomorphic SZ+  promote n+    | n < 0     = error "negative number"+    | otherwise =+        case promote (n - 1) of+          Monomorphic sn -> Monomorphic (SS sn)+  demote (Monomorphic sn) = toInt sn++data Vector (a :: *) (n :: Nat) where+  VNil :: Vector a Z+  (:-) :: a -> Vector a n -> Vector a (S n)++instance Monomorphicable (Vector a) whre+  type MonomorphicRep (Vector a) = [a]+  demote  (Monomorphic n) = toList n+  promote [] = Monomorphic Nil+  promote (x:xs) =+    case promote xs of+      Monomorphic xs' -> Monomorphic $ x :- xs'+```++`Monomorphic k` is the wrapper type to eliminate the polymorphic part of the types.+The `Monomorphicable` type-class provides the functions to convert polymorphic value from/to its monomorphic representation, say `MonomorphicRep k` associated type.++In the example above, `SNat n` can be monomorphically represented by `Int`.+There are some convenient functions to manipulate monomorphic types and functions. For more detail, see API documentation.

@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,25 @@+-- Initial monomorphic.cabal generated by cabal init.  For further +-- documentation, see http://haskell.org/cabal/users-guide/++name:                monomorphic+version:             0.0.1.0+synopsis:            Library to convert polymorphic datatypes to/from its monomorphic represetation+description:         This library provides the type-class and functions to convert between polymorphic data-types and its monomorphic representation type, such as length-indexed vectors, singletons for type-level natural numbers, etc.+homepage:            https://github.com/konn/monomorphic+license:             BSD3+license-file:        LICENSE+extra-source-files:  README.md+author:              Hiromi ISHII+maintainer:          konn.jinro_at_gmail.com+-- copyright:           +category:            Data+build-type:          Simple+cabal-version:       >=1.8+source-repository head+  Type: git+  Location: git://github.com/kazu-yamamoto++library+  exposed-modules:     Data.Type.Monomorphic+  -- other-modules:       +  build-depends:       base ==4.5.*, transformers ==0.3.*