Flow on FsFlow

FsFlow.Flow.apply

Mon, 01 Jan 0001 00:00:00 +0000

Applies a flow-wrapped function to a flow-wrapped value.

FsFlow.Flow.bind

Mon, 01 Jan 0001 00:00:00 +0000

Sequences a synchronous continuation after a successful value.

Remarks

This is the “flatmap” operation for Flow. It allows for dependent steps where the second flow depends on the value produced by the first.

Parameters

binder: A function that takes the successful value and returns a new flow.
flow: The source flow to sequence.

Returns

A Flow representing the combined workflow.

FsFlow.Flow.catch

Mon, 01 Jan 0001 00:00:00 +0000

Catches exceptions raised during execution and maps them to a typed error.

Remarks

Exceptions that are not caught by this helper will bubble up to the caller of run. This ensures that known exceptions can be handled within the flow context.

Parameters

handler: A function of type exn -> 'error to map the exception.
flow: The source flow of type Flow to monitor.

Returns

A Flow that converts exceptions into success-path errors.

FsFlow.Flow.delay

Mon, 01 Jan 0001 00:00:00 +0000

Defers flow construction until execution time.

FsFlow.Flow.env

Mon, 01 Jan 0001 00:00:00 +0000

Reads the current environment as the flow value.

Remarks

Use this when the entire environment object is needed for the next step of the workflow. For projecting specific properties, read is generally more ergonomic.

Returns

A Flow whose successful value is the current environment.

FsFlow.Flow.error

Mon, 01 Jan 0001 00:00:00 +0000

Creates a failing synchronous flow.

FsFlow.Flow.fail

Mon, 01 Jan 0001 00:00:00 +0000

Alias for error that reads well in some call sites.

Examples

let flow = Flow.fail "error"
 let result = Flow.run () flow
 // result = Failure (Cause.Fail "error")

FsFlow.Fiber

Mon, 01 Jan 0001 00:00:00 +0000

Represents a handle to a running workflow.

FsFlow.Builders.flow

Mon, 01 Jan 0001 00:00:00 +0000

The universal flow { } computation expression.

Remarks

Use this builder when the boundary can mix synchronous values, `Async`, `Task`, `Result`, and environment requests while keeping typed failures and explicit dependency access. It preserves the current environment model while allowing the workflow to compose task-oriented inputs directly, so callers do not need to switch builders just to cross an async boundary.

Examples

 let greeting =
     flow {
         let! name = Flow.env
         let! suffix = async { return "!" }
         return $"Hello, {name}{suffix}"
     }

FsFlow.Flow

Mon, 01 Jan 0001 00:00:00 +0000

Represents a cold workflow that reads an environment, returns a typed result, and is executed explicitly through Flow.run.

flow { }

Mon, 01 Jan 0001 00:00:00 +0000

The flow { } builder is the primary entry point for orchestrating synchronous, async, and task-based work.

Builder

FsFlow.Builders.flow: The universal flow { } computation expression.

FsFlow.Flow.fork

Mon, 01 Jan 0001 00:00:00 +0000

Starts a flow in a new fiber without waiting for it to complete.

Parameters

flow: The flow to fork.

Returns

A flow that produces a Fiber handle.

FsFlow.Flow.fromOption

Mon, 01 Jan 0001 00:00:00 +0000

Lifts an option into a synchronous flow with the supplied error.

Examples

let opt = Some "value"
 let flow = Flow.fromOption "missing" opt

FsFlow.Flow.fromResult

Mon, 01 Jan 0001 00:00:00 +0000

Lifts a Result into a synchronous flow.

Examples

let res = Ok "success"
 let flow = Flow.fromResult res

FsFlow.Flow.fromValueOption

Mon, 01 Jan 0001 00:00:00 +0000

Lifts a value option into a synchronous flow with the supplied error.

Parameters

error: The error to return if the value option is ValueNone.
value: The value option to lift.

Returns

A Flow that succeeds with the option’s value or fails with the provided error.

FsFlow.Flow.ignore

Mon, 01 Jan 0001 00:00:00 +0000

Maps the successful value of a synchronous flow to unit.

FsFlow.Flow.interrupt

Mon, 01 Jan 0001 00:00:00 +0000

Signals a fiber to stop and waits for it to finish its cleanup.

Parameters

fiber: The fiber to interrupt.

Returns

A flow that completes with the fiber’s final outcome after interruption.

FsFlow.Flow.join

Mon, 01 Jan 0001 00:00:00 +0000

Waits for a fiber to complete and returns its final outcome.

Parameters

fiber: The fiber to join.

Returns

A flow that completes with the fiber’s outcome.

FsFlow.Flow.localEnv

Mon, 01 Jan 0001 00:00:00 +0000

Transforms the environment before running the flow.

FsFlow.Flow.map

Mon, 01 Jan 0001 00:00:00 +0000

Maps the successful value of a synchronous flow.

Remarks

If the source flow fails, the mapper is not executed, and the error is preserved. This allows for safe transformation of data within the flow.

Parameters

mapper: A function of type 'value -> 'next to transform the successful value.
flow: The source flow of type Flow to transform.

Returns

A new Flow with the transformed success value of type 'next.

FsFlow.Flow.map2

Mon, 01 Jan 0001 00:00:00 +0000

Combines two flows with a mapping function.

FsFlow.Flow.map3

Mon, 01 Jan 0001 00:00:00 +0000

Combines three flows with a mapping function.

FsFlow.Flow.mapError

Mon, 01 Jan 0001 00:00:00 +0000

Maps the error value of a synchronous flow.

Remarks

Transforms the error type of the flow while leaving successful values untouched. Useful for mapping internal errors into public-facing domain errors.

Parameters

mapper: The function to transform the error value.
flow: The source flow.

Returns

A Flow with the transformed error type.

FsFlow.Flow.ok

Mon, 01 Jan 0001 00:00:00 +0000

Creates a successful synchronous flow.

FsFlow.Flow.orElse

Mon, 01 Jan 0001 00:00:00 +0000

Falls back to another flow when the source flow fails.

FsFlow.Flow.orElseFlow

Mon, 01 Jan 0001 00:00:00 +0000

Turns a pure validation result into a synchronous flow with environment-provided failure.

Remarks

This helper bridges the gap between pure validation (which often uses Result or Check) and the Flow environment model. If the result is an error, the provided errorFlow is executed to produce the final application error.

Parameters

errorFlow: A flow that reads the environment to produce an error value.
result: The pure result to bridge.

Returns

A Flow that mirrors the success of the result or fails with the outcome of the error flow.

FsFlow.Flow.orElseWith

Mon, 01 Jan 0001 00:00:00 +0000

Falls back to another flow when the source flow fails.

FsFlow.Flow.provideLayer

Mon, 01 Jan 0001 00:00:00 +0000

Provides a derived environment from a layer flow to a downstream flow.

FsFlow.Flow.race

Mon, 01 Jan 0001 00:00:00 +0000

Runs two flows concurrently and returns the result of the first one to complete.

Remarks

The “loser” flow is interrupted immediately.

FsFlow.Flow.read

Mon, 01 Jan 0001 00:00:00 +0000

Projects a value from the current environment.

Remarks

This is the primary way to access dependencies or configuration stored in the environment. The projection function is applied to the environment at execution time.

Parameters

projection: A function that extracts a value from the environment.

Returns

A Flow containing the projected value.

FsFlow.Flow.run

Mon, 01 Jan 0001 00:00:00 +0000

Executes a flow with the provided environment and the default cancellation token.

Examples

let flow = Flow.read (fun env -> $"Hello, {env}!")
 let result = Flow.run "World" flow
 // result = Effect that resolves to Success "Hello, World!" on both .NET and Fable

FsFlow.Flow.sequence

Mon, 01 Jan 0001 00:00:00 +0000

Transforms a sequence of flows into a flow of a sequence and stops at the first failure.

FsFlow.Flow.succeed

Mon, 01 Jan 0001 00:00:00 +0000

Alias for ok that reads well in some call sites.

Examples

let flow = Flow.succeed 42
 let result = Flow.run () flow
 // result = Success 42

FsFlow.Flow.tap

Mon, 01 Jan 0001 00:00:00 +0000

Runs a synchronous side effect on success and preserves the original value.

Remarks

Use this for logging, telemetry, or other “fire and forget” operations that should not alter the primary value path. If the binder flow fails, the entire flow fails with that error.

Parameters

binder: A function that produces a side-effect flow from the successful value.
flow: The source flow.

Returns

A Flow that preserves the original success value after the side effect.

FsFlow.Flow.tapError

Mon, 01 Jan 0001 00:00:00 +0000

Runs a synchronous side effect on failure and preserves the original error.

Remarks

Use this for error logging or cleanup actions that depend on the environment. If the binder side-effect flow itself fails, its error will overwrite the original error.

Parameters

binder: A function that produces a side-effect flow from the error value.
flow: The source flow.

Returns

A Flow that preserves the original error after the side effect.

FsFlow.Flow.traverse

Mon, 01 Jan 0001 00:00:00 +0000

Transforms a sequence of values into a flow and stops at the first failure.

FsFlow.Flow.value

Mon, 01 Jan 0001 00:00:00 +0000

Alias for ok that reads well in some call sites.

Examples

let flow = Flow.value "constant"

FsFlow.Flow.zip

Mon, 01 Jan 0001 00:00:00 +0000

Combines two flows into a tuple of their values.

FsFlow.Flow.zipPar

Mon, 01 Jan 0001 00:00:00 +0000

Combines two flows into a tuple of their values, running them concurrently.

Remarks

If either flow fails, the other is interrupted immediately.