ZipFold (empty) → 0.0

raw patch · 6 files changed

+183/−0 lines, 6 filesdep +TypeComposedep +basesetup-changed

Dependencies added: TypeCompose, base

Files

• Makefile +1/−0
• README +17/−0
• Setup.lhs +3/−0
• ZipFold.cabal +35/−0
• src/Data/Zip/FoldL.hs +114/−0
• wikipage.tw +13/−0

@@ -0,0 +1,1 @@+include ../conal-cabal-make.inc

@@ -0,0 +1,17 @@+ZipFold is a small package zipping folds, as described in a collection of+blog posts, <http://conal.net/blog/tag/zip>, inspired by the post "Beautiful Folds" by Max Rabkin+<http://squing.blogspot.com/2008/11/beautiful-folding.html>.++Please share any comments & suggestions on the discussion (talk) page at+[1].++You can configure, build, and install all in the usual way with Cabal+commands.++  runhaskell Setup.lhs configure+  runhaskell Setup.lhs build+  runhaskell Setup.lhs install++References:++[1] http://haskell.org/haskellwiki/ZipFold

@@ -0,0 +1,3 @@+#!/usr/bin/env runhaskell+> import Distribution.Simple+> main = defaultMain

@@ -0,0 +1,35 @@+Name:                ZipFold+Version:             0.0+Cabal-Version:       >= 1.2+Synopsis:            Zipping folds+Category:            Data+Description:+  ZipFold is a small package zipping folds, as described in a collection of+  blog posts, <http://conal.net/blog/tag/zip>, inspired by a post by Max Rabkin+  <http://squing.blogspot.com/2008/11/beautiful-folding.html>.+  .+  Project wiki page: <http://haskell.org/haskellwiki/ZipFold>+  .+  The module documentation pages have links to colorized source code and+  to wiki pages where you can read and contribute user comments.  Enjoy!+  .+  &#169; 2008 by Conal Elliott; BSD3 license.+Author:              Conal Elliott +Maintainer:          conal@conal.net+Homepage:            http://haskell.org/haskellwiki/ZipFold+Package-Url:         http://code.haskell.org/ZipFold+Copyright:           (c) 2008 by Conal Elliott+License:             BSD3+Stability:           experimental+build-type:          Simple++Library+  hs-Source-Dirs:      src+  Extensions:+  Build-Depends:       base, TypeCompose+  Exposed-Modules:     +                       Data.Zip.FoldL+                       +  ghc-options:         -Wall++--  ghc-prof-options:    -prof -auto-all 

@@ -0,0 +1,114 @@+{-# LANGUAGE ExistentialQuantification, FlexibleContexts #-}+{-# OPTIONS_GHC -Wall #-}+----------------------------------------------------------------------+-- |+-- Module      :  Data.Zip.FoldL+-- Copyright   :  (c) Conal Elliott 2008+-- License     :  BSD3+-- +-- Maintainer  :  conal@conal.net+-- Stability   :  experimental+-- +-- Zipping of non-strict left folds.+-- +-- Based on "Beautiful Folds" by Max Rabkin+-- <http://squing.blogspot.com/2008/11/beautiful-folding.html>+--+-- See also <http://conal.net/blog/posts/more-beautiful-fold-zipping>+----------------------------------------------------------------------++module Data.Zip.FoldL+  ( Fold(..), cfoldl, cfoldl'+  , WithCont , FoldC , cfoldlc+  , WithCont', FoldC', cfoldlc'+  , Pair'(..), P+  ) where++import Data.Monoid+import Control.Applicative+import Data.List (foldl')++import Data.Pair++-- | Data representation of a left fold+data Fold b a = F (a -> b -> a) a++-- | Interpretation of a 'Fold' as non-strict+cfoldl :: Fold b a -> [b] -> a+cfoldl (F op e) = foldl op e++-- Non-strict left-fold zipping+zipF :: Fold b a -> Fold b a' -> Fold b (a,a')+F op e `zipF` F op' e' = F op'' (e,e')+ where+   (a,a') `op''` b = (a `op` b, a' `op'` b)++instance Pair (Fold b) where pair = zipF++-- | Interpretation of a 'Fold' as non-strict+cfoldl' :: Fold b a -> [b] -> a+cfoldl' (F op e) = foldl' op e++-- Strict left-fold zipping+zipF' :: Fold b a -> Fold b a' -> Fold b (P a a')+F op e `zipF'` F op' e' = F op'' (P e e')+ where+   P a a' `op''` b = P (a `op` b) (a' `op'` b)+++instance Pair' (Fold b) where pair' = zipF'+++-- | Add a continuation.+data WithCont h b c = forall a. WC (h b a) (a -> c)++instance Functor (WithCont h b) where+  fmap g (WC f k) = WC f (fmap g k)++instance Pair (h b) => Applicative (WithCont h b) where+  pure a = WC (error "unneeded pre-cont") (pure a)+  WC f k <*> WC f' k' =+    WC (f `pair` f') (\ (a,a') -> (k a) (k' a'))+++-- | Non-strict left fold with continuation.+type FoldC = WithCont Fold++-- | Interpretation of a 'FoldC'+cfoldlc :: FoldC b a -> [b] -> a+cfoldlc (WC f k) = fmap k (cfoldl f)++++-- | Like 'WithCont' but with pair-strict '(<*>)'+data WithCont' h b c = forall a. WC' (h b a) (a -> c)++instance Functor (WithCont' h b) where+  fmap g (WC' f k) = WC' f (fmap g k)++instance Pair' (h b) => Applicative (WithCont' h b) where+  pure a = WC' (error "unneeded pre-cont") (pure a)+  WC' f k <*> WC' f' k' =+    WC' (f `pair'` f') (\ (P a a') -> (k a) (k' a'))++-- | Strict left fold with continuation.+type FoldC' = WithCont' Fold++-- | Interpretation of a 'FoldC'+cfoldlc' :: FoldC' b a -> [b] -> a+cfoldlc' (WC' f k) = fmap k (cfoldl' f)+++----++-- | Strict pairs+data P c c' = P !c !c'++-- | Strict generalized pair+class Pair' f where+  pair' :: f a -> f b -> f (P a b)++instance             Pair' []       where pair' = liftA2 P+instance Monoid u => Pair' ((,)  u) where pair' = liftA2 P+instance             Pair' ((->) u) where pair' = liftA2 P+instance             Pair' IO       where pair' = liftA2 P

@@ -0,0 +1,13 @@+[[Category:Packages]]++== Abstract ==++'''ZipFold''' is a small package zipping folds, as described in a [http://conal.net/blog/tag/zip collection of blog posts' and inspired by the post [http://squing.blogspot.com/2008/11/beautiful-folding.html "Beautiful Folds"] by Max Rabkin.++Besides this wiki page, here are more ways to find out about ZipFold:+* Visit the [http://hackage.haskell.org/cgi-bin/hackage-scripts/package/ZipFold Hackage page] for library documentation and to download & install.+* Or install with <tt>cabal install ZipFold</tt>.+* Get the code repository: <tt>darcs get http://code.haskell.org/ZipFold</tt>.+<!-- * See the [[ZipFold/Versions| version history]]. -->++Please leave comments at the [[Talk:ZipFold|Talk page]].