freewind

case class User(username:String, password: String)

trait UserRepositoryComponent {
  val userRepository: UserRepository
  
  class UserRepository {
    def authenticate(user: User): User = { 
      println("authenticating user: " + user)
      user
     }

freewind

case class User(username:String, password: String)

class UserRepository {
  def authenticate(user: User): User = { 
    println("authenticating user: " + user)
    user
   }
  def create(user: User) = println("creating user: " + user)
  def delete(user: User) = println("deleting user: " + user)
}

freewind

#!/bin/sh

# one way (older scala version will be installed)
# sudo apt-get install scala

#2nd way
sudo apt-get remove scala-library scala
wget http://www.scala-lang.org/files/archive/scala-2.11.1.deb
sudo dpkg -i scala-2.11.1.deb
sudo apt-get update

freewind

//
// The method `hello` in trait `A` and `B` are exactly same
//

object SameMethodInDifferentTraits {

  trait A {
    def hello()
  }

freewind

object TypesOfCompanion {

  class User

  object User

  def helloClass(user: User) = println(user)

  def helloObject(user: User.type) = println(user)

freewind

int led = 13;
int x = 4;

void setup() {                
  pinMode(led, OUTPUT);     
  pinMode(x, INPUT);
}

void loop() {
  int sta = digitalRead(x);

freewind

// curry的一个意义是: 方便scala根据第一组参数的内容,推断后面的类型
// scala采用基于流的局部推断,只会从第一组参数中获取类型信息,再用到其它组参数里
// 下面只有sort2不用写Int类型

def sort[T](f: (T,T)=>Boolean)(list:List[T]):List[T] = list
sort[Int]((x,y)=>true)(List(1,2,3))


def sort2[T](list:List[T])(f: (T,T)=>Boolean):List[T] = list

freewind

// curry的一个意义是: 方便scala根据第一组参数的内容,推断后面的类型
// scala采用基于流的局部推断,只会从第一组参数中获取类型信息,再用到其它组参数里
// 下面只有sort2不用写Int类型

def sort[T](f: (T,T)=>Boolean)(list:List[T]):List[T] = list
sort[Int]((x,y)=>true)(List(1,2,3))


def sort2[T](list:List[T])(f: (T,T)=>Boolean):List[T] = list

freewind

def double(number:Int) = 2*number
def add10(number:Int) = 10 + number
def negative(number:Int) = -1 * number

def myconvert(n:Int) = Some(n).map(double).map(add10).map(negative).get

myconvert(5)

freewind

import scala.io.Source.stdin

object App {
  def main(args: Array[String]) {
    stdin.getLines foreach { line =>
      println(myconvert(line.toInt))
    }
  }
  
  val double = (number:Int) => 2*number