Bind Mappings

This pages shows you which computation expressions can implicitly bind to other CEs

Example

Here we can bind an 'T Option to 'T AsyncOption without having to lift from one type to another. See here for a better understanding on 'lifting'. To associate with the table below, the AsyncOption is the CE and the Option is the CE that can bind to it.

asyncOption {
    let! x = Some 1 
    return x
}

Note

Each CE can bind to itself so we don't list that here to reduce clutter

CE	Can Bind
AsyncOption	Async, Task, Option
AsyncResult	Result, Choice, Async, Task, TaskResult
AsyncResultOption	TaskResultOption, AsyncResult, TaskResult, AsyncOption, Result, Choice, Async, Task, Option,
AsyncValidation	AsyncResult, Validation, Result, Choice, Async
CancellableTaskResult	ValueTaskResult, AsyncResult, TaskResult, AsyncChoice, CancellableTask, ColdTask, Result, Choice, Async, Task
CancellableTaskValidation	AsyncValidation, ValueTaskResult, AsyncResult, TaskResult, AsyncChoice, CancellableTask, ColdTask, Validation, Result, Choice, Async, Task
JopOption	TaskOption, AsyncOption, Job, Async, Task, Option
JobResult	AsyncResult, TaskResult, Job, Result, Choice, Async, Task
JobResultOption
Option	ValueOption, nullable object
Result	Choice
ResultOption	Result, Choice, Option
Task
TaskOption	ValueTaskOption, AsyncOption, PlyOption, Async, Task, ValueTask, Option
TaskResult	AsyncResult, PlyResult, TaskResult, ValueTaskResult, Result, Choice, Ply, Async, Task, ValueTask
TaskResultOption
Validation	Result, Choice

Don't see the bindings you want?

Luckily the CEs are extensible so you can add your own Source overloads to the builders. Take for example the AsyncOption builder. Let's pretend it didn't support being able to bind Async values. You can add an overload as follows shown below. The code shown would go in your own codebase, unless you'd want to submit a PR 😉 If you need an example of how to do this with various syntax, check out any of the CE files in the codebase.

module MyCustomCodeModule =

    type AsyncOptionBuilder with
        member _.Source(value: Async<'T>) : Async<'T option> =
           value |> Async.map Some