lub 0.0.6 → 0.1.1

raw patch · 3 files changed

+166/−3 lines, 3 filesdep ~unambPVP ok

version bump matches the API change (PVP)

Dependency ranges changed: unamb

API changes (from Hackage documentation)

Files

• lub.cabal +7/−3
• src/Data/Glb.hs +92/−0
• src/Data/Lazier.hs +67/−0

@@ -1,7 +1,7 @@ Name:                lub-Version:             0.0.6+Version:             0.1.1 Cabal-Version:       >= 1.2-Synopsis:            least upper bounds -- information merging+Synopsis:            information operators: least upper bound (lub) and greatest lower bound (glb) Category:            Concurrency, Data, Other Description:   Lub is an experiment in computing least upper information bounds on@@ -11,6 +11,8 @@   neither is bottom, 'lub' is able to synthesize a value from the   partial information contained in both of its arguments.   .+  This module also defines 'glb', which intersects information.+  .   Project wiki page: <http://haskell.org/haskellwiki/lub>   .   &#169; 2008 by Conal Elliott; BSD3 license.@@ -26,10 +28,12 @@ Library   hs-Source-Dirs:      src   Extensions:-  Build-Depends:       base < 5, unamb >= 0.1.3+  Build-Depends:       base < 5, unamb >= 0.2.4   Exposed-Modules:                             Data.Repr                        Data.Lub+                       Data.Glb+                       Data.Lazier                           ghc-options:         -Wall 

@@ -0,0 +1,92 @@+-- {-# LANGUAGE #-}+{-# OPTIONS_GHC -Wall #-}+----------------------------------------------------------------------+-- |+-- Module      :  Data.Glb+-- Copyright   :  (c) Conal Elliott 2010+-- License     :  BSD3+-- +-- Maintainer  :  conal@conal.net+-- Stability   :  experimental+-- +-- Greatest lower bound+----------------------------------------------------------------------++module Data.Glb (HasGlb(..),glbBottom,flatGlb) where++import Control.Applicative (liftA2)++import Data.Repr++-- | Types that support information intersection ('glb')+class HasGlb a where+  -- | Greatest lower information bound.  Intersects information available+  -- from each argument.+  glb  :: a -> a -> a+  -- | n-ary 'lub'.  Defaults to @foldr lub undefined@+  glbs :: [a] -> a+  glbs = foldr glb undefined++-- | Bottom for a 'glb'.  In the form of @error \"glb: bottom (\<reason\>)\"@,+-- though not really an error.+glbBottom :: String -> a+glbBottom msg = error $ "glb: bottom (" ++ msg ++ ")"++-- | 'glb' on flat types with equality.  Gives bottom for unequal+-- arguments.+flatGlb :: Eq a => a -> a -> a+flatGlb a b | a == b    = a+            | otherwise = glbBottom "flat & unequal"++-- Flat types:+instance HasGlb ()      where glb = flatGlb+instance HasGlb Bool    where glb = flatGlb+instance HasGlb Char    where glb = flatGlb+instance HasGlb Int     where glb = flatGlb+instance HasGlb Integer where glb = flatGlb+instance HasGlb Float   where glb = flatGlb+instance HasGlb Double  where glb = flatGlb+-- ...++instance (HasGlb a, HasGlb b) => HasGlb (a,b) where+  (a,b) `glb` (a',b') = (a `glb` a', b `glb` b')++instance HasGlb b => HasGlb (a -> b) where+  glb = liftA2 glb++instance (HasGlb a, HasGlb b) => HasGlb (Either a b) where+  Left  a `glb` Left  a' = Left  (a `glb` a')+  Right b `glb` Right b' = Right (b `glb` b')+  _ `glb` _ = glbBottom "glb: bottom (Left/Right mismatch)"+++-- 'glb' on representations+repGlb :: (HasRepr a v, HasGlb v) => a -> a -> a+repGlb = onRepr2 glb++-- instance (HasRepr t v, HasGlb v) => HasGlb t where+--   glb = repGlb++-- For instance,+instance HasGlb a => HasGlb (Maybe a) where glb = repGlb+instance HasGlb a => HasGlb [a]       where glb = repGlb++{- -- Examples++-- It takes care to check that some of these examples are computed+-- correctly, since printing stops at the first error.  For instance, ask+-- for t5!!1 .++t1,t2 :: Int+t1 = 6 `glb` 8  -- _|_+t2 = 7 `glb` 7  -- 7++t3,t4 :: (Int,Int)+t3 = (3,4) `glb` (4,5)  -- (_|_,_|_)+t4 = (3,4) `glb` (3,5)  -- (3,_|_)++t5 :: [Int]+t5 = [2,3,5] `glb` [1,3]  -- _|_:3:_|_++-}+

@@ -0,0 +1,67 @@+-- {-# LANGUAGE #-}+{-# OPTIONS_GHC -Wall #-}+----------------------------------------------------------------------+-- |+-- Module      :  Data.Lazier+-- Copyright   :  (c) Conal Elliott 2010+-- License     :  BSD3+-- +-- Maintainer  :  conal@conal.net+-- Stability   :  experimental+-- +-- Some lazier operations.+-- See <http://conal.net/blog/posts/lazier-functional-programming-part-2/>+----------------------------------------------------------------------++module Data.Lazier (eitherL,condL) where++import Data.Lub+import Data.Glb++condL :: (HasLub a, HasGlb a) =>+         a -> a -> Bool -> a+condL a b = const (a `glb` b) `lub` (\ c -> if c then a else b)++eitherL :: (HasLub c, HasGlb c) =>+           (a -> c) -> (b -> c) -> (Either a b -> c)+eitherL f g = const (f undefined `glb` g undefined) `lub` either f g++{- -- Examples:++-- It takes care to check that some of these examples are computed+-- correctly, since printing stops at the first error.  For instance, ask+-- for t5!!1 .++q :: Int+q = undefined `unamb` 5++t0 :: Int+t0 = condL 3 4 True++t1,t2 :: Int+t1 = condL 6 8 undefined  -- _|_+t2 = condL 7 7 undefined  -- 7++t3,t4 :: (Int,Int)+t3 = condL (3,4) (4,5) undefined  -- (_|_,_|_)+t4 = condL (3,4) (3,5) undefined  -- (3,_|_)++t5 :: [Int]+t5 = condL [2,3,5] [1,3] undefined  -- _|_:3:_|_+++fe1 :: Either Float Bool -> (Int,String)+fe1 = eitherL (\ x -> (3,"beetle " ++ show x)) (\ b -> (3,"battle " ++ show b))++s1 :: (Int,String)+s1 = fe1 undefined+-- (3,"b*** Exception: glb: bottom (flat & unequal)++s2 :: String+s2 = (tail.tail.tail.snd) (fe1 undefined)+-- "tle *** Exception: Prelude.undefined++s3 :: (Int,String)+s3 = fe1 (Left pi)++-}