Add book for parallelAsyncValidation

Author: njlr

gitbook/parallelAsyncResult/ce.md

@@ -4,7 +4,7 @@ Namespace: `FsToolkit.ErrorHandling`
 
 This CE operates on the same type as `asyncResult`, but it adds the `and!` operator for running workflows in parallel.
 
-Concurrent workflows are run with the same semantics as [`Async.Parallel`](https://fsharp.github.io/fsharp-core-docs/reference/fsharp-control-fsharpasync.html#Parallel), so only the first exception is returned.
+When running concurrent workflows, fail-fast semantics are used. If any sub-task returns an `Error`, then all other tasks are cancelled and only that error is returned. To instead collect all errors, use `parallelAsyncValidation`.
 
 
 ## Examples

gitbook/parallelAsyncValidation/ce.md

@@ -0,0 +1,37 @@
+## ParallelAsyncValidation Computation Expression
+
+Namespace: `FsToolkit.ErrorHandling`
+
+This CE operates in the same way as `asyncValidation`, except that the `and!` operator will run workflows in parallel.
+
+Concurrent workflows are run with the same semantics as [`Async.Parallel`](https://fsharp.github.io/fsharp-core-docs/reference/fsharp-control-fsharpasync.html#Parallel).
+
+
+## Examples
+
+See [here](../validation/ce.md) for other validation-like examples
+
+```fsharp
+// Result<string, string> -> Async<Result<string, string>>
+let downloadAsync stuff = async {
+    return stuff
+}
+
+// AsyncValidation<string, string>
+let addResult = parallelAsyncValidation {
+    let! x = downloadAsync (Ok "I")
+    and! y = downloadAsync (Ok "am")
+    and! z = downloadAsync (Ok "concurrent!")
+    return sprintf "%s %s %s" x y z
+}
+// async { return Ok "I am concurrent!" }
+
+// AsyncValidation<string, string>
+let addResult = parallelAsyncValidation {
+    let! x = downloadAsync (Error "Am")
+    and! y = downloadAsync (Error "I")
+    and! z = downloadAsync (Error "concurrent?")
+    return sprintf "%s %s %s" x y z
+}
+// async { return Error [ "Am"; "I"; "concurrent?" ] }
+```

gitbook/parallelAsyncValidation/map2.md

@@ -0,0 +1,14 @@
+## ParallelAsyncValidation.map2
+
+Namespace: `FsToolkit.ErrorHandling`
+
+Function Signature:
+
+```fsharp
+('a -> 'b -> 'c)
+  -> Async<Result<'a, 'd list>>
+  -> Async<Result<'b, 'd list>>
+  -> Async<Result<'c, 'd list>>
+```
+
+Like [ParallelAsyncResult.map2](../parallelAsyncResult/map2.md), but collects the errors from both arguments.

gitbook/parallelAsyncValidation/map3.md

@@ -0,0 +1,16 @@
+## ParallelAsyncValidation.map3
+
+Namespace: `FsToolkit.ErrorHandling`
+
+Function Signature:
+
+```
+('a -> 'b -> 'c -> 'd)
+  -> Async<Result<'a, 'e list>>
+  -> Async<Result<'b, 'e list>>
+  -> Async<Result<'c, 'e list>>
+  -> Async<Result<'d, 'e list>>
+```
+
+Like [ParallelAsyncResult.map3](../parallelAsyncResult/map3.md), but collects the errors from all arguments.
+