IO Effect

The IO effect allows for running side-effecting operations while maintaining referential transparency.

Overview

The IO effect provides a guard rail to uncontrolled exceptions by lifting functions into the world of effectful computations.

Basic Usage

import in.rcard.yaes.IO.*

case class User(name: String)

def saveUser(user: User)(using IO): Long =
  throw new RuntimeException("Read timed out")

Handlers

Non-blocking Handler

Returns a Future without blocking the current thread:

import in.rcard.yaes.IO.*
import scala.concurrent.Future
import scala.concurrent.ExecutionContext.Implicits.global

val result: Future[Long] = IO.run {
  saveUser(User("John"))
}

Blocking Handler

Blocks the current thread until completion:

import in.rcard.yaes.IO.*
import scala.concurrent.ExecutionContext.Implicits.global

val result: Long = IO.blockingRun {
  saveUser(User("John"))
}

Implementation Details

• Uses Java Virtual Threads for execution
• Each effectful computation runs in a new virtual thread
• Handlers break referential transparency and should be used only at application edges

Best Practices

• Use IO for any operation that might throw exceptions
• Combine with other effects like Raise for better error handling
• Keep handlers at the application boundary