Getting Started

Getting Started with λÆS

Requirements

• Java 25 or higher is required to run λÆS due to its use of modern Java features like Virtual Threads and Structured Concurrency.
• Scala 3 is required, as λÆS leverages Scala 3’s context functions and other advanced features.

Installation

The library is available on Maven Central. Add the following dependencies to your build.sbt:

libraryDependencies ++= Seq(
  "in.rcard.yaes" %% "yaes-core"        % "0.16.0",
  "in.rcard.yaes" %% "yaes-data"        % "0.16.0", // Optional: Flow and data structures
  "in.rcard.yaes" %% "yaes-cats"        % "0.16.0", // Optional: Cats Effect integration
  "in.rcard.yaes" %% "yaes-slf4j"       % "0.16.0", // Optional: SLF4J logging backend
  "in.rcard.yaes" %% "yaes-http-server" % "0.16.0", // Optional: HTTP server
  "in.rcard.yaes" %% "yaes-http-circe"  % "0.16.0"  // Optional: Circe JSON for HTTP
)

The library is only available for Scala 3 and is currently in an experimental stage. The API is subject to change.

Modules

• yaes-core: Essential effects for functional programming (Sync, Async, Raise, etc.)
• yaes-data: Functional data structures that work with effects (Flow, etc.)
• yaes-cats: Cats Effect 3 integration for bidirectional interop
• yaes-slf4j: SLF4J logging backend for the Log effect
• yaes-http-server: HTTP server built on λÆS effects and virtual threads
• yaes-http-circe: Circe JSON integration for the HTTP server

Your First Effect

Let’s start with a simple example using the Random and Raise effects:

import in.rcard.yaes.Random.*
import in.rcard.yaes.Raise.*

def flipCoin(using Random, Raise[String]): String = {
  val result = Random.nextBoolean
  if (result) "Heads" else "Tails"
}

Running Effects

To execute the effectful computation, use handlers:

import in.rcard.yaes.Random.*
import in.rcard.yaes.Raise.*

val result: String = Raise.run {
  Random.run {
    flipCoin
  }
}

Next Steps

• Read Core Concepts to understand the mental model behind λÆS
• Explore Basic Effects to learn about Sync, Random, I/O, and Clock effects
• Jump to Error Handling once you are comfortable with the basics