MateuszKubuszok

Tagged, refined and newtypes for Scala

Because we have too few solutions

Library	Docs	Types	Integrations	Notes
built-in	official	AnyVal extended by class with a single value	many libraries support AnyVals	- Scala 2/3, but on 3 it has a replacement

soujiro32167

//> using scala 3.6.3

import scala.deriving.Mirror
import scala.compiletime.{erasedValue}

/** Type-level function that transforms a type-level tuple of types
  * into a corresponding tuple of List[...] at the value level.
  *
  * E.g., if Ts is (T1, T2, T3), Partitioned[Ts] is (List[T1], List[T2], List[T3]).
  */

jodersky

import scala.deriving._
import scala.compiletime.{erasedValue, summonInline}

// super primitive (but composable via typeclass derivation) JSON reader
trait Reader[A] {
  def read(json: ujson.Value): A
}
object Reader {

  given Reader[Int] = new Reader[Int] {

calvinlfer

Understanding Covariance and Contravariance

There are at least 3 aspects to consider when dealing with contravariance and covariance when using container types.

def example(x: Container[T]): Container[T]

1. What can you feed in
2. What can point to the result
3. What can the function return

jdegoes

object test {
  import scalaz.zio._

  type UserID = String
  case class UserProfile(name: String)

  // The database module:
  trait Database {
    val database: Database.Service

dacr

// summary : Just ONE ammonite script file to execute a load performance test using gatling !
// keywords : scala, gatling, ammonite, scala, load-test, performance
// publish : gist
// authors : David Crosson
// license : Apache NON-AI License Version 2.0 (https://raw.githubusercontent.com/non-ai-licenses/non-ai-licenses/main/NON-AI-APACHE2)
// id : ea7a4259-9461-44a8-99fa-1ec6ec3c48ed
// created-on : 2018-09-22T07:41:07Z
// managed-by : https://github.com/dacr/code-examples-manager
// execution : scala ammonite script (http://ammonite.io/) - run as follow 'amm scriptname.sc'

danilbykov

import cats.effect.ExitCase._
import cats.effect.Sync
import cats.effect.concurrent.Ref
import cats.syntax.flatMap._
import cats.syntax.functor._

trait Tap[F[_]] {
  def apply[A](effect: F[A]): F[A]
}

gvolpe

import cats.Traverse
import cats.effect._
import cats.effect.concurrent.Semaphore
import cats.temp.par._
import cats.syntax.all._

import scala.concurrent.duration._

object Main extends IOApp {
  import ParTask._

mpilquist

// Alternative to sealed abstract case class pattern for Scala 2.12.2+
// Benefits:
//  - 1 final class instead of 1 sealed class + anonymous subclass
//  - portable to Scala 3 regardless of opaque types
//  - less boilerplate

final case class Angle private (toDegrees: Int) {
  // Define our own `copy` method to suppress synthetic one
  // Add private to prevent it from being used
  def copy(degrees: Int = toDegrees): Angle = Angle.fromDegrees(degrees)

arosien

Variance: OOP vs. FP

TODO: introduction

Note: the examples below use the following algebraic data type:

sealed trait Shape
case class Circle(radius: Double) extends Shape
case class Rectangle(height: Double, width: Double) extends Shape