lagenorhynque

// expressions as a type class
trait Expr[repr: Type -> Type] {
    pub def int(n: Int32): repr[Int32]
    pub def bool(b: Bool): repr[Bool]
    pub def add(e1: repr[Int32], e2: repr[Int32]): repr[Int32]
    pub def mul(e1: repr[Int32], e2: repr[Int32]): repr[Int32]
    pub def eq(e1: repr[a], e2: repr[a]): repr[Bool] with Eq[a]
}

// an evaluator

lagenorhynque

enum Person({ name = String, age = Int32 })

instance ToString[Person] {
    pub def toString(p: Person): String = match p {
        case Person.Person({ name, age }) =>
            "Person(name = ${name}, age = ${age})"
    }
}

def example(): Unit \ IO =

lagenorhynque

use Sys.Process

// The main entry point.
def main(): Unit \ { Process, Abort, IO } =
    println("Hello World!");

    let n = 5;
    println("The square of ${n} is ${square(n)}.");

    runProcess()

lagenorhynque

slides:
  charset: utf-8
  theme: night
  highlight_theme: monokai-sublime
  separator_vertical: ^\s*----\s*$
revealjs:
  transition: convex
plugins:
  - extra_css:
    - https://cdnjs.cloudflare.com/ajax/libs/meyer-reset/2.0/reset.min.css

lagenorhynque

lagenorhynque

Kotlinでミニマルな

Result実装による

関数型エラーハンドリング

#KotlinFest_SSK

---

lagenorhynque

Functional Calisthenics

in Kotlin

Kotlinで「関数型エクササイズ」を実践しよう

#KotlinFest

---

lagenorhynque

(ns arith
  (:require
   [clojure.spec.alpha :as s]))

;;; definition of terms
;;; <term> ::= true
;;;          | false
;;;          | (if <term> <term> <term>)
;;;          | <number>
;;;          | (+ <term>*)

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> :{