programaker

import eu.timepit.refined.api.{Refined, Validate}
import eu.timepit.refined.boolean.{And, Not}
import eu.timepit.refined.refineV

/* Domain types */

final case class Customer(id: Long, name: String, age: Int)
final case class Order(description: String)

//===

programaker

import cats.Monad
import cats.syntax.functor.*
import cats.effect.IO
import cats.effect.unsafe.implicits.global

case class Frunfles(id: Long, name: String)

trait DatabaseConnection:
  def exec[F[_]: Monad](op: String): F[Unit]

programaker

// $ scalac Test.scala
// and then
// $ javap -c Test$
object Test {
  def s1: String =
    "aaa" +
      "/bbb" +
      "/ccc"

  def s2: String = {

programaker

trait DataSource[A] {
  def source: Option[A]
}
object DataSource {
  implicit val EvenIntDataSource: DataSource[Int] = new DataSource[Int] {
    import scala.util.Random
    
    override def source: Option[Int] =
      Some(Random.between(100, 1000)).filter(_ % 2 == 0)
  }

programaker

//Functional programming is all about:

//. Pure, total and deterministic functions
//. ADTs (Algebraic Data Types)
//. Typeclasses

//However, in hybrid languages like Scala, OOP classes can still play a role!

//---------------------------------------------------------

programaker

/*** Type-safety through Phantom types ***/

sealed trait Status
object Status {
  case object Enabled extends Status
  case object Disabled extends Status

  //Using type aliases to avoid `Object.type` spreading all over the code
  type Enabled = Enabled.type
  type Disabled = Disabled.type

programaker

class Producer[+X](x: X) {
  def produce: X = x
}

class Consumer[-X](name: String) {
  def consume(x: X): Unit = println(s">>> $name is consuming $x polimorfically")
}

//--------------------------------------

programaker

# If you come from bash you might have to change your $PATH.
# export PATH=$HOME/bin:/usr/local/bin:$PATH

# Path to your oh-my-zsh installation.
export ZSH="$HOME/.oh-my-zsh"

# Set name of the theme to load --- if set to "random", it will
# load a random theme each time oh-my-zsh is loaded, in which case,
# to know which specific one was loaded, run: echo $RANDOM_THEME
# See https://github.com/ohmyzsh/ohmyzsh/wiki/Themes

programaker

"Monads are Monoids in the Category of Endofunctors"

If you are a functional programmer, you've probably heard this statement before.

To understand it, first we need to understand its component parts:
. Category
. Monoid
. Endofunctor

After this, we will glue those parts together piece by piece to grasp the whole.

programaker

//Functional programming is programming combining functions.
//
//We have a bunch of simple functions, then combine them into 
//more and more complex functions until have a full program.
//
//The simplest case is when the functions are COMPOSABLE, for example, given the functions:
f: A => B
g: B => C 
h: C => D