timjb

module Main (main) where

import Control.Monad (forM_)

-- | Given the length l of a cord from points A to B on the unit circle, compute
-- the length of the cords A-C and C-B, where C is the point on the unit circle
-- exactly in between A and B.
iterArchimedes :: Double -> Double
iterArchimedes l = l / sqrt (2 + sqrt (4 - l*l))

timjb

Copyright Tim Baumann (c) 2016

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.

timjb

pijul.org
sanakirja

timjb

Installing Pijul on macOS

Prerequisites

$ brew install openssl libssh
$ export LIBRARY_PATH=/usr/local/lib OPENSSL_LIB_DIR=/usr/local/opt/openssl/lib OPENSSL_INCLUDE_DIR=/usr/local/opt/openssl/include DEP_OPENSSL_INCLUDE=/usr/local/opt/openssl/include

Installing from crates.io

timjb

Nachtrag zum [FTypes-Vortrag beim Curry Club Augsburg][youtube]:

HasFType

Ich habe gezeigt, wie man mit FTypes einen bidirektionalen JSON-Parser für den Datentyp FGithubUser Identity schreiben kann. Nun ist das ja ein etwas unhandlicher Record-Datentyp, weil alle seine Feld-Werte noch mit dem Identity-Funktor gewrappt sind. Deshalb will man auch noch einen "ganz normalen" Datentyp

data GithubUser
  = GithubUser
  { userLogin :: T.Text

, userId :: GithubUserId

timjb

{-# LANGUAGE ExplicitForAll #-}

module WorksOnlyWithoutScopedTypeVariables where

myMap :: forall a b. (a -> b) -> [a] -> [b]
myMap = myMapWithSwappedVariables
  where
    myMapWithSwappedVariables :: (b -> a) -> [b] -> [a]
    myMapWithSwappedVariables = fmap
    

timjb

#!/usr/bin/env stack
-- stack --resolver lts-6.4 --install-ghc runghc --package primitive --package hashable --package vector

module HashTable where

import Prelude hiding (lookup)
import Control.Monad.Primitive (PrimMonad (..))
import Data.Hashable (Hashable (..))
import qualified Data.List as L
import qualified Data.Vector.Mutable as VM

timjb

#!/usr/bin/env stack
-- stack --resolver lts-6.4 --install-ghc runghc --package unordered-containers --package QuickCheck --package hashable

{-# LANGUAGE GeneralizedNewtypeDeriving #-}

module DiffMonoid where

import Data.Hashable (Hashable)
import Data.Monoid ((<>))
import Test.QuickCheck

timjb

{-# LANGUAGE FlexibleInstances #-}
{-# LANGUAGE KindSignatures #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE StandaloneDeriving #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE ViewPatterns #-}

timjb

module PatternSynonymsImport where

-- one can use either an unqualified import
import PatternSynonymsTest
-- alternatively one can use explicit imports (this requires enabling the
-- PatternSynonyms language extension):
-- import PatternSynonymsTest (Option(..), pattern None)

maybeToOption :: Maybe a -> Option a
maybeToOption Nothing = None