okapies

import scala.runtime.ScalaRunTime

/**
 * A sample code to implement a customized case class manually (for Scala 2.9.2 final).
 *
 * Id has two properties: name and displayName. 'displayName' has default value that
 * is same value as 'name'.
 */
class Id private ( // make primary constructor not to be accessible. (standard case class can do)

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-- usage: joinProb $ fmap sort flipThree
--        joinProb $ fmap (all (==Tails)) flipThree

import Control.Monad
import Data.Function (on)
import Data.List (groupBy, sortBy)
import Data.Ord (comparing)
import Data.Ratio

newtype Prob a = Prob { getProb :: [(a, Rational)] } deriving Show

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命令型のコールバック、関数型のプロミス: Node が逸した最大の機会

Original: "Callbacks are imperative, promises are functional: Node's biggest missed opportunity" by James Coglan

Translated by Yuta Okamoto (@okapies)

Note

• 訳者は JavaScript や Node.js に関する専門知識がほとんどありません。識者のツッコミをお待ちしております。「◯◯が分からない」等も歓迎です。
• 元記事から構成を一部変更しています。また、関数型プログラミングに関する記述のうち、議論の骨子に絡まないものは省略しています。

okapies

// value class
class Param(val i: Int) extends AnyVal

implicit def asParam(i: Int) = Param(i)

// followings are invalid because `Param` is a final class.

case class AnyParam(_i: Int) extends Param(_i)

case object ConstantA extends Param(-1)

okapies

import breeze.linalg._

/*
 * p.15 (http://nineties.github.io/math-seminar/7.html#/15)
 * 
 * Note: Does breeze basically recommend side effects?
 * Note: The compiler will complain 'could not find implicit value for parameter canMapValues'
 *       if you make the type parameter 'Int' as a generic type.
 */
def matAdd(a: DenseMatrix[Int], b: DenseMatrix[Int]) =

okapies

class HogeOps(val underlying: Any) extends AnyVal {
  private
    [this] // <-- !!!
    def toOption[A](v: => A): Option[A] = ???
}

okapies

import java.io.BufferedReader
import java.io.InputStreamReader
import scala.annotation.tailrec

import org.joda.time._
import com.github.tototoshi.slick.H2JodaSupport._

object MessageLogger extends App {

  val profile = scala.slick.driver.H2Driver

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FP in Scala chapter notes - Chapter 11: Monads

The original is licensed using the MIT license.

Eilenberg-Moore 圏

モナドのもう一つの圏論的な見方は Eilenberg-Moore 圏だ。モナドの EM 圏は、モナドの代数の圏だ。

例えば、List モナドの代数は Scala の Monoid だ。List モナドの EM 圏は、モノイドを対象 (object) としモノイド準同型（10 章を参照）を射 (arrow) とする圏だ。

okapies

[
  {
    "name": "Ergo-JIS layout",
    "author": "@okapies",
    "switchMount": "cherry",
    "switchBrand": "gateron",
    "switchType": "KS-3-Red",
    "pcb": true
  },
  [

okapies

[
  {
    "name": "Ergo-JIS layout",
    "author": "@okapies",
    "switchMount": "cherry",
    "switchBrand": "gateron",
    "switchType": "KS-3-Red",
    "pcb": true
  },
  [