atacratic

This tutorial explains how Unison handles 'effectful' computations, like storing state or performing I/O, using abilities. It assumes you haven't come across abilities before, and covers everything from the ground up.

This is an unofficial tutorial, written before the one on unisonweb.org/docs. The approach taken here is slow and methodical. Your first stop should be the official tutorial, if you haven't seen it already.

This doc is a Unison transcript - the source is here.

Terminology note: other languages with ability systems typically call them 'effect handlers' or 'algebraic effects', but many of the ideas are the same.

Introducing abilities

agolovenko

final case class InformationSize(size: Double, unit: InformationUnit) extends Ordered[InformationSize] {
  import InformationSize.{safeAdd, safeDivide, safeMultiply}
  import InformationUnit._

  if (size < 0d) throw new IllegalArgumentException(s"Unsupported negative size: $size")

  def toBits: Double      = to(Bit)
  def toKiloBits: Double  = to(KiloBit)
  def toMegaBits: Double  = to(MegaBit)
  def toBytes: Double     = to(Byte)