joost-de-vries

Java 8 definitely took some 'oomph' out of mainstream Scala adoption. I do see a lot of Scala adoption at the moment though. Currently it's mostly in ecommerce.

For me Java 8 is too little too late. The things I really miss in Java 8 are:

• pattern matching Not only handling the cases but more importantly deconstructing the object into variables.
• type inferencing To prevent Javas so called type stutter SessionFactory sessionFactory = createSessionFactory();. And also to not have to type tedious generic declarations like

Map<String, Observable<JsonNode>> observableMap = stream.collect(mapCollector);

joost-de-vries

object foldfun {

  def foldr[A, B](f: A => B => B)(b: B)(s: Seq[A]): B = s match {
    case Nil => b
    case a :: as =>
      f(a)(foldr(f)(b)(as))
  }                                               //> foldr: [A, B](f: A => (B => B))(b: B)(s: Seq[A])B

  foldr { a: String => b: Int => a.toInt * b.toInt }(7)(Seq("1", "2", "3"))
                                                  //> res0: Int = 42

joost-de-vries

#!/bin/bash
#
# =========================================================================
# Copyright 2014 Rado Buransky, Dominion Marine Media
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0

joost-de-vries

[error] /home/vagrant/wendwet/core/src/main/scala/annoteren/model/objectrollen.scala:78: overloaded method value format with alternatives:
[error]   [T(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)](w: play.api.libs.json.Writes[T(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)])(implicit r: play.api.libs.json.Reads[T(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)])play.api.libs.json.OFormat[T(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)] <and>
[error]   [T(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)(in method format)](r: play.api.libs.json.Reads[

joost-de-vries

a semigroup is addable

a monoid is foldRightable or aggregatable
(ie addable, zero)

a functor is mappable
 
a monad is chainable or flatmappable

strong suit of monads:

joost-de-vries

import scala.language.higherKinds
import play.api.libs.functional.InvariantFunctor
 
object JsonCombinatorUtil {
/** workaround voor issue dat json combinators niet kunnen omgaan met case classes met 1 veld
* zie http://stackoverflow.com/questions/15042205/how-to-serialize-deserialize-case-classes-to-from-json-in-play-2-1 */
implicit class FormatBuilder[M[_], A](o: M[A]) {
 def build[B](f1: A => B, f2: B => A)(implicit fu: InvariantFunctor[M]) =
  fu.inmap[A, B](o, f1, f2)
 }