mandubian

// That compiles for real in a patched version of Scala just introducing the KindPolymorphic syntax
object Test {
  // Basic Kind polymorphism sample
  trait Foo[T <: KindPolymorphic] { type Out ; def id(t: Out): Out = t }

  object Foo {
    implicit def foo0[T] = new Foo[T] { type Out = T }
    implicit def foo1[T[_]] = new Foo[T] { type Out = T[Any] }
    implicit def foo2[T[_, _]] = new Foo[T] { type Out = T[Any, Any] }
  }

djspiewak

sealed trait Task[A] {
  import Task._

  final def flatMap[B](f: A => Task[B]): Task[B] = Suspend(this, f)

  final def map[B](f: A => B): Task[B] = this match {
    case Suspend(inner, suspension) =>
      Suspend(inner, suspension andThen { _ map f })

    case Async(body) =>

djspiewak

Getting Started in Scala

This is my attempt to give Scala newcomers a quick-and-easy rundown to the prerequisite steps they need to a) try Scala, and b) get a standard project up and running on their machine. I'm not going to talk about the language at all; there are plenty of better resources a google search away. This is just focused on the prerequisite tooling and machine setup. I will not be assuming you have any background in JVM languages. So if you're coming from Python, Ruby, JavaScript, Haskell, or anywhere…  I hope to present the information you need without assuming anything.

Disclaimer It has been over a decade since I was new to Scala, and when I was new to Scala, I was coming from a Java and Ruby background. This has probably caused me to unknowingly make some assumptions. Please feel free to call me out in comments/tweets!

One assumption I'm knowingly making is that you're on a Unix-like platform. Sorry, Windows users.

Getting the JVM

travisbrown

class TC[A](val x: String)

object TC {
  def getX[A: TC](a: A): String = implicitly[TC[A]].x

  implicit def anyTC[A]: TC[A] = new TC[A]("*")
  implicit val stringTC: TC[String] = new TC[String]("String")
}

object Example {

cb372

import scala.reflect.macros.blackbox

object PrettyPrinting {

  /* 
   * Print a raw AST, nicely indented. 
   * Pretty fragile, e.g. will get confused by string literals containing commas or parentheses.
   */
  def prettyTree(raw: String): String = {
    var level = 0

larsrh

# Uses Alex Archambault's coursier launcher
# Download as follows:
# $ curl -L -o coursier https://git.io/vgvpD && chmod +x coursier
# ... or refer to instructions here: <https://github.com/alexarchambault/coursier>

# list any dependencies here
COURSIER_CLASSPATH="$(coursier fetch -p com.chuusai:shapeless_2.11:2.3.1)"

# this downloads and launches tut in a seperate step
# the 'classpath' argument is being interpreted by scalac

jbgi

package scalaz

import org.openjdk.jmh.annotations._

@Fork(1)
@BenchmarkMode(Array(Mode.Throughput))
class AdtEncodingsBench {

  import AdtEncodingsBench._

jdegoes

Applied Functional Programming with Scala - Notes

Copyright © 2016-2018 Fantasyland Institute of Learning. All rights reserved.

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

paulp

% sbtx dependencyGraph
... blah blah ...
[info] *** Welcome to the sbt build definition for Scala! ***
[info] Check README.md for more information.
[error] Not a valid command: dependencyGraph
[error] Not a valid project ID: dependencyGraph


% sbtx -Dplugins=graph dependencyGraph
... blah blah ...

raulraja

import scala.concurrent.ExecutionContext.global

for {
  a <- nonBlocking
  b <- simpleDbLookups   
  c <- expensiveDbLookups
  d <- dbWriteOperations
  e <- expensiveCpuOperations
} yield result