halcat0x15a

extern crate regex;
use regex::Regex;

#[derive(Debug)]
enum ParseResult<T> {
    Success { result: T, next: String },
    Failure
}

impl<T> ParseResult<T> {

halcat0x15a

一つの型に対して2つのインスタンスを提供する

• 値のwrap/unwrapがない
• インスタンスの定義が単純
• インスタンスが一意に定まらない

コンパニオンオブジェクトの同一階層に複数のimplicit valueを定義した場合

• importが必須
• エラーがわかりづらい（could not find implicit value）

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object GADTs {

  sealed trait Data1[A]
  case class Constructor1() extends Data1[Int]

  sealed trait Data2 { type T }
  case class Constructor2() extends Data2 { type T = Int }

  def f1[A](data: Data1[A]): A = data match { case Constructor1() => 0 }
  //def f2[A](data: Data2 { type T = A }): A = data match { case Constructor2() => 0 }

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import scala.annotation.tailrec

sealed abstract class Var {

  def walk(subst: Subst): Var = {
    @tailrec
    def go(v: Var, stack: List[Var], acc: Option[Var]): Var =
      v match {
        case Unbound(k) =>
          subst.get(k) match {

halcat0x15a

import scala.annotation.tailrec

sealed abstract class Queue[U <: Union, -A, +B] {

  def apply(a: A): Free[U, B] = {
    @tailrec
    def go(tpe: { type T })(arrows: Queue[U, tpe.T, B], value: tpe.T): Free[U, B] =
      arrows.view match {
        case One(f) => f(value)
        case cons@Cons() =>

halcat0x15a

package kits.free

import scala.annotation.tailrec

sealed abstract class Queue[R[_], -A, +B] {

  def :+[C](f: B => Free[R, C]): Queue[R, A, C] = new Node(this, new Leaf(f))

  def ++[C](that: Queue[R, B, C]): Queue[R, A, C] = new Node(this, that)

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import scala.annotation.tailrec

sealed abstract class Queue[F[_], A, B] {

  def :+[C](f: B => F[C]): Queue[F, A, C] =
    new Node(this, new Leaf(f))

  def ++[C](that: Queue[F, B, C]): Queue[F, A, C] =
    new Node(this, that)

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  @tailrec
  def go[F[_], A, B](arg: (Queue[F, A, T], Queue[F, T, B]) forSome { type T }): View[F, A, B] = {
    arg match {
      case (Leaf(v), y) => new Cons(v, y)
      case (Node(l, r), y) => go[F, A, B](l, Node(r, y))
    }
  }

halcat0x15a

Backtracking, Interleaving, and Terminating Monad Transformers

halcat0x15a@Oleg勉強会

http://okmij.org/ftp/Computation/LogicT.pdf

Abstract

halcat0x15a

!SLIDE

ScalaとOpenCVとAkka HTTPとReact.jsで作る麻雀点数計算アプリケーション

halcat0x15a

!SLIDE

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