plur (empty) → 0.1.0.0

raw patch · 5 files changed

+119/−0 lines, 5 filesdep +basedep +semigroupssetup-changed

Dependencies added: base, semigroups

Files

• ChangeLog.md +5/−0
• LICENSE +30/−0
• Setup.hs +2/−0
• plur.cabal +21/−0
• src/Data/Plur.hs +61/−0

@@ -0,0 +1,5 @@+# Revision history for plur++## 0.1.0.0  -- YYYY-mm-dd++* First version. Released on an unsuspecting world.

@@ -0,0 +1,30 @@+Copyright (c) 2018, Joel Burget++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 Joel Burget 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 +1,2 @@+import Distribution.Simple+main = defaultMain

@@ -0,0 +1,21 @@+name:                plur+version:             0.1.0.0+synopsis:            Plurality monad: Zero, one, or at least two.+-- description:+license:             BSD3+license-file:        LICENSE+author:              Joel Burget+maintainer:          joelburget@gmail.com+copyright:           (c) 2018 Joel Burget+category:            Data+build-type:          Simple+extra-source-files:  ChangeLog.md+cabal-version:       >=1.10++library+  exposed-modules:     Data.Plur+  build-depends:+    base >=4.11 && <4.12,+    semigroups >= 0.18+  hs-source-dirs:      src+  default-language:    Haskell2010

@@ -0,0 +1,61 @@+{-# language LambdaCase #-}+module Data.Plur (Plur(..), count) where++import Data.Monoid+import Data.Semigroup++-- Plurality monad: Zero, one, or at least two.+data Plur a+  = Zero+  | One a+  | Two a a+  deriving (Show, Eq, Ord)++instance Functor Plur where+  fmap f = \case+    Zero      -> Zero+    One a     -> One (f a)+    Two a1 a2 -> Two (f a1) (f a2)++instance Applicative Plur where+  pure = One++  (<*>) Zero _        = Zero+  (<*>) _ Zero        = Zero+  (<*>) (One f) x     = fmap f x+  (<*>) (Two f1 f2) x = fmap f1 x <> fmap f2 x++instance Monad Plur where+  (>>=) x f = case x of+    Zero      -> Zero+    One x1    -> f x1+    Two x1 x2 -> f x1 <> f x2++instance Foldable Plur where+  foldMap f = \case+    Zero      -> mempty+    One a     -> f a+    Two a1 a2 -> f a1 <> f a2++instance Traversable Plur where+  traverse f = \case+    Zero      -> pure Zero+    One a     -> One <$> f a+    Two a1 a2 -> Two <$> f a1 <*> f a2++instance Semigroup (Plur a) where+  r1      <> Zero    = r1+  Zero    <> r2      = r2+  One x   <> One y   = Two x y+  One x   <> Two y _ = Two x y+  Two x _ <> One y   = Two x y+  Two x _ <> Two y _ = Two x y++instance Monoid (Plur a) where+  mempty = Zero++count :: Plur a -> Int+count = \case+  Zero    -> 0+  One _   -> 1+  Two _ _ -> 2