open System
open System.IO
open System.Threading
open System.Threading.Tasks
open Axial
open Axial.Layers
open Axial.Console
open Axial.FileSystem
open Axial.Hosting
open Axial.Hosting.Browser
open Axial.Hosting.Node
open Axial.PlatformService
open Axial.State
open Axial.Telemetry
open Axial.Telemetry.JavaScript

Composing Streams

Composition builds a larger stream without starting any source.

Append

FlowStream.append consumes the left stream before the right stream:

> (FlowStream.fromSeq [ 1; 2 ] : FlowStream<int>)
- |> FlowStream.append (FlowStream.fromSeq [ 3; 4 ])
- |> FlowStream.runCollect
- |> Flow.run ();;

val it: Exit<int list,Never> = Success [1; 2; 3; 4]

The right side is not pulled while the left side still has values.

Map and flatten

FlowStream.collect maps each value to an inner stream and flattens those streams in order. This is the stream equivalent of flatMap or monadic bind:

> (FlowStream.fromSeq [ 1; 2; 3 ] : FlowStream<int>)
- |> FlowStream.collect (fun value ->
- FlowStream.fromSeq [ value; value * 10 ])
- |> FlowStream.runCollect
- |> Flow.run ();;

val it: Exit<int list,Never> = Success [1; 10; 2; 20; 3; 30]

Each inner stream completes before the next outer value is expanded.

Zip

FlowStream.zip pulls one value from each side and stops when either side completes:

> (FlowStream.fromSeq [ 1; 2; 3 ] : FlowStream<int>)
- |> FlowStream.zip (FlowStream.fromSeq [ "a"; "b" ])
- |> FlowStream.runCollect
- |> Flow.run ();;

val it: Exit<Tuple<int,string> list,Never> = Success [(1, "a"); (2, "b")]

The result contains two pairs. The remaining value from the longer side is not emitted.

Lifetimes inside composition

A composed stream may own several upstream resources. Natural completion closes a source when it finishes, while the terminal consumer's child scope is the final safety boundary for failure, interruption, and early termination. See Scopes for the ownership model.