FxList

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Effectful iteration over collections — each element can trigger effects within the current handler context.

FxList (general)

Full effect support, including Yield and Suspend:

results <- FxList.fx_map(users, fn user ->
  details <- Repo.get(UserDetail, user.id)
  {:ok, %{user | details: details}}
end)

total <- FxList.fx_reduce(items, 0, fn item, acc ->
  price <- PriceService.lookup(item.sku)
  {:ok, acc + price}
end)

_ <- FxList.fx_each(users, fn user ->
  Writer.tell(:audit, {:processed, user.id})
end)

active <- FxList.fx_filter(users, fn user ->
  sub <- Repo.get(Subscription, user.id)
  {:ok, sub.status == :active}
end)

FxFasterList (performance)

Higher throughput (~0.1 µs/op vs ~0.2 µs/op for FxList). Limited Yield support — best for effectful operations that don't suspend:

result <- FxFasterList.fx_map(items, &process/1)

Both are pure combinators — no handler needed. They iterate through each element, running the provided effectful function, collecting results.

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