NOTE: This is an article by Chris Taylor, originally posted on his blog, but the blog was removed at some point. I resurected it from the WayBack Machine without the authors permission, but post it here for posterity's sake, so others may be able to find it.
by Chris Taylor
FEB 10TH, 2013
| import Data.Array (snoc) | |
| import Data.Either (Either(..)) | |
| rights :: forall a b. Array (Either a b) -> Array b | |
| rights array = | |
| let | |
| f (Left _) accumulator = accumulator | |
| f (Right value) accumulator = snoc accumulator value | |
| in | |
| foldr f [] array |
| import Data.Either (Either(..), either, hush) | |
| import Data.Array (mapMaybe) | |
| import Data.Maybe (Maybe(..)) | |
| rights :: forall a b. Array (Either a b) -> Array b | |
| rights array = mapMaybe hush array | |
| -- Also the Lefts implementation | |
| lefts :: forall a b. Array (Either a b) -> Array a | |
| lefts array = mapMaybe (either Just (const Nothing)) array |
| import Data.Array | |
| import Data.Array.ST (empty, push, freeze) | |
| import Data.Either (Either(..)) | |
| import Control.Monad.ST.Internal (ST, foreach) | |
| -- Return Rights from an Array of Either's using the ST monad | |
| rights :: forall a b. Array (Either a b) -> Array b | |
| rights array = | |
| let | |
| -- This seems to be required because |
| //How can we do this imperitive process with Haskell/Purescript style functions? | |
| //Examples | |
| // > generateQuestions([1,2,3,4,5,6,7,8])(3)(2) | |
| // [ [ 1, 2, 3 ], [ 4, 5, 6 ] ] | |
| // > generateQuestions([1,2,3,4,5])(2)(4) | |
| // [ [ 1, 2 ], [ 3, 4 ], [ 5, 1 ], [ 2, 3 ] ] |
| using System; | |
| using System.Linq; | |
| using System.Collections.Generic; | |
| namespace DearCSharpYouLose { | |
| public static class FuncExtension { | |
| public static Func<A, C> Select<A, B, C>(this Func<A, B> f, Func<B, C> g) { | |
| return a => g(f(a)); | |
| } |
| {-# OPTIONS_GHC -fwarn-incomplete-patterns -Werror #-} | |
| -- Show | |
| -- p1 = | |
| -- ... | |
| -- method(f,f) | |
| -- ... | |
| -- p2 = | |
| -- ... |
| //Local Declaration | |
| Func<string> returnsString = () => ""; | |
| Func<int, int> takesIntReturnsInt = i => i * 2; | |
| //Class-Level Declaration | |
| //Generic Params |
| Download `cabal-install-2.2.0.0-x86_64-apple-darwin-sierra.tar.gz` | |
| Extract | |
| Run: | |
| Gregs-MacBook-Pro:downloads huck$ ./cabal --version | |
| cabal-install version 2.2.0.0 | |
| compiled using version 2.2.0.1 of the Cabal library | |
| Gregs-MacBook-Pro:downloads huck$ ./cabal install Cabal cabal-install | |
| Warning: Parsing the index cache failed (Unknown encoding for constructor). | |
| Trying to regenerate the index cache... |