propensive

object Unpack:
  import scala.quoted._
  import scala.compiletime._

  private def tupleType(s: String)(using q: Quotes): q.reflect.TypeRepr =
    import q.reflect._
    val typeParams =
      s.map{ c =>
        TypeRepr.of(using ConstantType(CharConstant(c)).asType)
      }.toList

propensive

// Define the general Arg type and companion object:
import language.higherKinds, language.implicitConversions, language.existentials
object Arg { implicit def toArg[Tc[_], T: Tc](t: T): Arg[T, Tc] = Arg(t, implicitly[Tc[T]]) }
case class Arg[T, Tc[_]](value: T, typeclass: Tc[T])

// Say, for example we have a typeclass for getting the length of something, with a few instances
trait Lengthable[T] { def length(t: T): Int }
implicit val intLength = new Lengthable[Int] { def length(i: Int) = 1 }
implicit val stringLength = new Lengthable[String] { def length(s: String) = s.length }

propensive

A short journey through types in Scala

(based on the Jon Pretty's "Advanced Type Mechanics" workshop)

Type

It is a named collection of method signatures. Those method signatures are called properties.

Classes and traits vs types

We should be careful not to confuse classes or traits and types, because they are different things. Every class and trait gives rise to a type with the same name, but in itself is not a type. Many types also exist which do not solely correspond to a trait or a class.

propensive

import magnolia.{CaseClass, Magnolia, SealedTrait}
import org.specs2.matcher.describe._

import scala.language.experimental.macros

object DiffableDerivation {

  /** binds the Magnolia macro to this derivation object */
  implicit def genDiffable[T]: Diffable[T] = macro Magnolia.gen[T]

propensive

### Keybase proof

I hereby claim:

  * I am propensive on github.

  * I am propensive (https://keybase.io/propensive) on keybase.

  * I have a public key ASArWRtQnt8y3AuDBYD0B3FsCtq6W4pRE0tAl6GhlZMAcAo

propensive

object Algebra {

  // Build up increasingly complex algebras
  trait Magma[T] {
    def add(x : T, y : T) : T
  }

  trait Monoid[T] extends Magma[T] {
    def zero : T
  }

propensive

Welcome to Scala version 2.11.7 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_45).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import rapture.xml._
import rapture.xml._

scala> import xmlBackends.stdlib._
import xmlBackends.stdlib._

propensive

magnolia/one:
00:01.388187   src/foo.scala
00:04.130835   src/magnolia/one.scala
00:01.339720   src/magnolia/one.scala
00:00.893572   src/magnolia/one.scala
00:00.640120   src/magnolia/one.scala
00:00.664193   src/magnolia/one.scala
00:00.608714   src/magnolia/one.scala
00:00.502048   src/magnolia/one.scala
00:00.497764   src/magnolia/one.scala

propensive

import rapture.io._

// Let's parse some JSON
val src: Json = Json.parse("""
{
  "foo": "Hello world",
  "bar": {
    "baz": 42
  }
}

propensive

Welcome to Scala version 2.10.2 (Java HotSpot(TM) 64-Bit Server VM, Java 1.6.0_24).
Type in expressions to have them evaluated.
Type :help for more information.

scala> import rapture.core._
import rapture.core._

scala> import rapture.json._
import rapture.json._