hatashiro

module Main where

import Prelude
import Control.Monad.Eff.Console (log)
import Debug.Trace (trace)

f :: Int -> String
f 1 = "one"
f 2 = "two"
f _ = "meh"

hatashiro

This is a modified version of the patch found here:
https://gist.github.com/choppsv1/36aacdd696d505566088

Which itself is a modified version of:
http://emacs.1067599.n5.nabble.com/RFC-Add-tty-True-Color-support-tt299962.html

To use true-color, use the flag --color=true-color.

Alternatively, set the EMACS_TRUE_COLOR_SEPARATOR environment variable to
either ':' or ';'.

hatashiro

module Main where

import Control.Applicative
import Data.Monoid
import Test.QuickCheck
import Test.QuickCheck.Checkers
import Test.QuickCheck.Classes

instance Monoid a => Monoid (ZipList a) where
  mempty = pure mempty

hatashiro

module Main where

import Control.Applicative
import Data.Monoid
import Test.QuickCheck
import Test.QuickCheck.Checkers
import Test.QuickCheck.Classes

instance Monoid a => Monoid (ZipList a) where
  mempty = pure mempty

hatashiro

{-# LANGUAGE ExistentialQuantification #-}
{-# LANGUAGE Rank2Types #-}
{-# LANGUAGE TypeOperators #-}

module Main where

-- | 'f ~> g' means natural transformation from a functor 'f' to a functor 'g'
type (~>) f g = forall a. f a -> g a

-- | const functor, which works as if it's just a constant

hatashiro

import Test.Hspec
import Test.Hspec.QuickCheck (prop)

main :: IO ()
main = hspec $ do
  describe "quickcheck" $ do
    prop "assoc" $ \x y z ->
      x + (y + z) == ((x + y) + (z :: Double))

hatashiro

Let me guess there is a data PL as a sum type of records:

data PL = Functional { name :: String, pure :: Bool }
        | ObjectOriented { name :: String, multipleInheritance :: Bool }

The type of pure is:

hatashiro

{-# LANGUAGE OverloadedStrings #-}
{-# OPTIONS_GHC -fno-warn-unused-do-bind #-}
import Control.Applicative ((<$>), (<*>))
import Data.Maybe (isJust)

import Data.Text (Text)
import Text.Blaze ((!))

hatashiro

You can read this in my blog too.

http://noraesae.net/2016/10/14/reader-monad-and-function-composition/

---

Reader monad and Function Composition

Let me guess we're about to filter a list of integers, xs.

hatashiro

timestampPath :: IO FilePath
timestampPath = ???

-- using do, more readable.
writeTimestamp :: UnixTime -> IO ()
writeTimestamp x = do
  path <- timestampPath
  writeFile path (encodeUnixTime x)
  
-- using point-free style, feeling good.