lagenorhynque

module Factorial where

factorial :: Integral a => a -> a
factorial 0 = 1
factorial n = n * factorial (n - 1)

factorialSeq :: Integral a => [a]
factorialSeq = scanl (*) 1 [1..]

lagenorhynque

λ> data Box a = Box a deriving (Show, Eq)
type Box :: * -> *
data Box a = ...
-- Functorの実装
λ> :{
λ| instance Functor Box where
λ|     fmap f (Box x) = Box $ f x
λ| :}
-- Applicativeの実装
λ> :{

lagenorhynque

関数型言語テイスティング

Haskell, Scala, Clojure, Elixirを

比べて味わう関数型プログラミングの旨さ

#fp_matsuri

#fp_matsuri_c

lagenorhynque

(ns money
  (:refer-clojure :exclude [+])
  (:require
   [clojure.spec.alpha :as s])
  (:import
   (java.util
    Currency)))

(s/def ::amount nat-int?)
(s/def ::currency #(instance? Currency %))

lagenorhynque

module MyPrelude where

import Prelude hiding (filter, foldl, foldr, map, reverse)

foldLeft :: (b -> a -> b) -> b -> [a] -> b
foldLeft _ acc [] = acc
foldLeft f acc (x:xs) = foldLeft f (f acc x) xs

reverse' :: [a] -> [a]
reverse' = foldLeft (flip (:)) []

lagenorhynque

純LISPから考える

関数型言語のプリミティブ

Clojure, Elixir, Haskell, Scala

#lispmeetup

---

lagenorhynque

From Scala/Clojure

to Kotlin

#serverside_kotlin_meetup

---

lagenorhynque

scala> enum ShippingCategory:
     |   case UsLocalState, UsRemoteState, International
     | 
// defined class ShippingCategory
                                                                                                                                                                                        
scala> object Address:
     |   class AddressInfo(val country: String, val state: String)
     | 
     |   def apply(country: String, state: String) = AddressInfo(country, state)
     | 

lagenorhynque

#!/usr/bin/env bash

# npm install -g reveal-md

reveal-md tdd-with-rdd.md --theme night --highlight-theme monokai-sublime -w $@

lagenorhynque

(ns clj-tdd-with-rdd.core
  (:require
   [clojure.spec.alpha :as s]
   [clojure.string :as str]))

(s/fdef fizzbuzz
  :args (s/cat :n pos-int?)
  :ret string?)

(defn fizzbuzz [n]