HoleyMonoid (empty) → 0.1

raw patch · 4 files changed

+112/−0 lines, 4 filesdep +basesetup-changed

Dependencies added: base

Files

• Data/HoleyMonoid.hs +59/−0
• HoleyMonoid.cabal +27/−0
• LICENSE +24/−0
• Setup.hs +2/−0

@@ -0,0 +1,59 @@+-- | Monoids with holes. The 'HoleyMonoid' allows building monoidal values of which certain components are to be filled in later. For example:+--+-- > > let holey = now "x = "+-- >             . later show+-- >             . now ", y = "+-- >             . later show+-- > > run holey 3 5+-- > "x = 3, y = 5"+--+-- This module is intended to be imported in qualified fashion, e.g.+--+-- > import qualified Data.HoleyMonoid as HM++module Data.HoleyMonoid (+  HoleyMonoid, run,+  now, later, map+  +  ) where++import Prelude hiding (id, (.), map)+import Control.Category+import Data.Monoid++-- | The type of a monoid with holes. The underlying monoid is represented by+-- type parameter @m@. The @r@ is the result type and stays polymorphic until the+-- very last moment when 'run' is called. The last argument @a@ is always a+-- function with zero or more arguments, finally resulting in @r@. Ordering the+-- arguments in this order allows holey monoids to be composed using `.`, stacking the+-- expected arguments. Note that the `Monoid` constraint is only used in the+-- identity 'HoleyMonoid' and in composing two 'HoleyMonoid's.+newtype HoleyMonoid m r a = HoleyMonoid { runHM :: (m -> r) -> a }++instance Monoid m => Category (HoleyMonoid m) where+  id    = now mempty+  f . g = f `bind` \a -> g `bind` \b -> now (a `mappend` b)++-- | Insert a constant monoidal value.+now :: m -> HoleyMonoid m r r+now a = HoleyMonoid ($ a)++-- | Monadic indexed bind for holey monoids.+bind :: HoleyMonoid m b c -> (m -> HoleyMonoid n a b) -> HoleyMonoid n a c+m `bind` f = HoleyMonoid $ \k -> runHM m (\a -> runHM (f a) k)++-- | Insert a monoidal value that is not specified until the computation is+-- 'run'. The argument that is expected later is converted to the monoid type+-- using the given conversion function.+later :: (a -> m) -> HoleyMonoid m r (a -> r)+later f = HoleyMonoid (. f)++-- | Convert between underlying 'Monoid' types.+map :: (m -> n) -> HoleyMonoid m r a -> HoleyMonoid n r a+map g m = HoleyMonoid (\k -> runHM m (k . g))++-- | Run the computation, resulting in a function that still expects some+-- arguments. The number of arguments that is still expected will be equal to the+-- number of 'later's the computation is built of.+run :: HoleyMonoid m m a -> a+run m = runHM m id

@@ -0,0 +1,27 @@+Name:           HoleyMonoid+Version:        0.1+Synopsis:       Monoids with holes.+Description:   	The 'HoleyMonoid' allows building monoidal values of which certain components are to be filled in later. For example:+                .+                > > let holey = now "x = "+                >             . later show+                >             . now ", y = "+                >             . later show+                > > run holey 3 5+                > "x = 3, y = 5"++Author:         Martijn van Steenbergen+Maintainer:     Martijn van Steenbergen <martijn@van.steenbergen.nl>+Stability:      Experimental+Copyright:      Some Rights Reserved (CC) 2009 Martijn van Steenbergen+Homepage:       http://code.google.com/p/monoid-cont/++Cabal-Version:  >= 1.2+License:        BSD3+License-file:   LICENSE+Category:       Data Structures+Build-type:     Simple++Library+  Exposed-Modules:  Data.HoleyMonoid+  Build-Depends:    base >= 4, base < 5

@@ -0,0 +1,24 @@+Copyright (c) 2009, Martijn van Steenbergen+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 the author nor the+      names of his contributors may be used to endorse or promote products+      derived from this software without specific prior written permission.++THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 <copyright holder> 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 +1,2 @@+import Distribution.Simple+main = defaultMain