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object NonDefaultResources {
  implicit object MySpecificUrlResource extends Resource[URL] {
    // ...
  }
}

def main(args: Array[String]) {
  import NonDefaultResources.MySpecificUrlResource

  println("Children of URL: \n: " +

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// Ad 1) Type class trait ("utility" rozhraní, na které budou 
// adaptovány konkrétní zdroje):
trait Resource[R] {
  def hasChildren(res: R): Boolean
  def children(res: R): Seq[R]
}

// Ad 2) Companion object s výchozími implicitními implementacemi
// type class traitu pro URL a File: 
object Resource {

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package com.examples.img

import java.io.File
import scala.sys.process._

class ImageMagickConverter(convertExec: String) {

  def resizeImage(in: File, out: File, width: Int, height: Int, quality: Int = ImageMagickConverter.DefaultQuality): Boolean = {
    val qual = if (quality < 0) ImageMagickConverter.DefaultQuality else if (quality > 100) 100 else quality
    val inAbsPath = in.getAbsolutePath()

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package controllers

import play.api.mvc.Action
import play.api.mvc.Controller
import scala.concurrent.future
import scala.concurrent.ExecutionContext.Implicits.global
import play.api.Logger

object Performance extends Controller {

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concurrent.Future {
  // Nejaky blokujici kod pristupujici k databazi
}(Contexts.myDbOperationContext)

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play {
  my-db-context {
    fork-join-executor {
      parallelism-factor = 1.0
      parallelism-max = 200
    }
  }
}

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object Contexts {
  implicit val myDbOperationContext: ExecutionContext = 
    Akka.system.dispatchers.lookup("my-db-context")
}

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import play.api.libs.concurrent.Execution.Implicits._

def someAsyncAction = Action {
  Async {
    WS.get("http://www.someservice.com").get().map { 
      response =>
        Ok("Response code: " + response.status)
    }
  }
}

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import Contexts.myDbOperationContext
concurrent.Future {
  // Nejaky blokujici kod pristupujici k databazi
}

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package dojo

import java.net.URL
import java.io.File
import scala.io.Source
import java.io.InputStream
import scala.util.Try
import scala.util.Success

trait Resource[R] {