ReaderTaskEither

The ultimate composition: DI + async + error handling

What is ReaderTaskEither?

ReaderTaskEither combines three powerful patterns: Reader for dependency injection, Task for async operations, and Either for error handling. This is the ultimate type for production applications that need all three.

// Instead of mixing concerns:
async function process(id) {
  const config = global.config
  try { ... } catch (e) { ... }
}

// Use RTE:
const process: RTE<Config, Error, Result> = ...
ask
flatMap
mapLeft
local
parallel
🎯

Triple Power

Reader + Task + Either combined

🚀

Production Ready

Real-world app architecture

🧪

Testable

Mock dependencies easily

✅

Type-Safe

Dependencies, errors, async all typed

ReaderTaskEither in Action

❌ Mixing Concerns

async function processData(id: number) {
  const config = getGlobalConfig()
  try {
    const data = await fetchData(config, id)
    return transform(data)
  } catch (error) {
    return null
  }
}

✅ ReaderTaskEither

const processData = (id: number): RTE<Config, Error, Data> =>
  pipe(
    RTE.ask<Config>(),
    RTE.chain(config => fetchData(config, id)),
    RTE.map(transform)
  )

// DI + Async + Errors all typed

Practice Exercises

1

Basic

Learn about basic in fp-ts readertaskeither

beginnerStart
2

Ask

Learn about ask in fp-ts readertaskeither

beginnerStart
3

Map

Learn about map in fp-ts readertaskeither

beginnerStart
4

Chain

Learn about chain in fp-ts readertaskeither

intermediateStart
5

Local

Learn about local in fp-ts readertaskeither

intermediateStart
6

Mapleft

Learn about mapleft in fp-ts readertaskeither

intermediateStart
7

Parallel

Learn about parallel in fp-ts readertaskeither

advancedStart
8

Practical

Learn about practical in fp-ts readertaskeither

advancedStart

Why Learn ReaderTaskEither?

🎯

Master ReaderTaskEither

Learn the fundamental concepts and patterns that make ReaderTaskEither powerful

💪

8 Exercises

Practice with hands-on exercises from advanced level

🚀

Production Ready

Apply ReaderTaskEither patterns to build robust, type-safe applications