nagyadam2092/fp-ts_vs_effect.md

## fp-ts_vs_effect.md

      
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              fp-ts_vs_effect.md
            
          
Feature
fp-ts (Task/TaskEither)
Effect


Async primitive
Task<A> = () => Promise<A> (lazy)
Effect<Out, Err, Req> (runnable via runPromise, etc.)


Error channel
TaskEither<E, A> = () => Promise<Either<E, A>>
Dedicated error channel in Effect<Out, Err, Req>


Exception wrapping
tryCatch wraps thrown/rejected Promises into Left<E>
Effect.try / Effect.tryPromise wrap sync/async functions


Composition
pipe, chain, map, fold on TaskEither
.pipe(Effect.map, Effect.chain, Effect.catchAll, …)


Concurrency
No built-in fibers; manual via Promise.all
First-class fibers with safe cancellation (Effect.fork)


Retry / Backoff
No built-in support; manual retries
Schedule library offers retry policies out of the box


Resource safety (bracketing)
Manual try/finally around Task or TaskEither
Effect.acquireRelease / Effect.bracket for cleanup


Dependency injection & layers
None (custom Context needed)
Built-in Context and Layer modules


Bundle size
Very small; type-level constructs, tree-shakeable
Larger core runtime plus optional modules; tree-shakeable


Learning curve
Steep for HKTs and FP type classes
Steeper initial investment, but consistent for large systems
Feature	fp-ts (Task/TaskEither)	Effect
Async primitive	`Task<A> = () => Promise<A>` (lazy)	`Effect<Out, Err, Req>` (runnable via `runPromise`, etc.)
Error channel	`TaskEither<E, A> = () => Promise<Either<E, A>>`	Dedicated error channel in `Effect<Out, Err, Req>`
Exception wrapping	`tryCatch` wraps thrown/rejected Promises into `Left<E>`	`Effect.try` / `Effect.tryPromise` wrap sync/async functions
Composition	`pipe`, `chain`, `map`, `fold` on `TaskEither`	`.pipe(Effect.map, Effect.chain, Effect.catchAll, …)`
Concurrency	No built-in fibers; manual via `Promise.all`	First-class fibers with safe cancellation (`Effect.fork`)
Retry / Backoff	No built-in support; manual retries	Schedule library offers retry policies out of the box
Resource safety (bracketing)	Manual `try/finally` around `Task` or `TaskEither`	`Effect.acquireRelease` / `Effect.bracket` for cleanup
Dependency injection & layers	None (custom Context needed)	Built-in Context and Layer modules
Bundle size	Very small; type-level constructs, tree-shakeable	Larger core runtime plus optional modules; tree-shakeable
Learning curve	Steep for HKTs and FP type classes	Steeper initial investment, but consistent for large systems
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