add gitbook pages

Author: JayWearsSocks

gitbook/option/sequenceAsyncResult.md

@@ -0,0 +1,31 @@
+## Option.sequenceAsyncResult
+
+Namespace: `FsToolkit.ErrorHandling`
+
+Function Signature:
+
+```fsharp
+Async<Result<'a, 'e>> option -> Async<Result<'a option>, 'e>
+```
+
+Note that `sequence` is the same as `traverse id`. See also [Option.traverseAsyncResult](traverseAsyncResult.md).
+
+See also Scott Wlaschin's [Understanding traverse and sequence](https://fsharpforfunandprofit.com/posts/elevated-world-4/).
+
+## Examples
+
+### Example 1
+
+```fsharp
+let r1 : Async<Result<int option, string>> =
+  Some (async { return Ok 42 }) |> Option.sequenceAsyncResult 
+// async { return Ok (Some 42) }
+
+let r2 : Async<Result<int option, string>> =
+  Some (async { return Error "something went wrong" }) |> Option.sequenceAsyncResult 
+// async { return Error "something went wrong" }
+
+let r3 : Async<Result<int option, string>> =
+  None |> Option.sequenceAsyncResult 
+// async { return Ok None }
+```

gitbook/option/traverseAsyncResult.md

@@ -0,0 +1,44 @@
+## Option.traverseAsyncResult
+
+Namespace: `FsToolkit.ErrorHandling`
+
+Function Signature:
+
+```fsharp
+('a -> Async<Result<'b,'c>>) -> 'a option -> Async<Result<'b option, 'c>>
+```
+
+Note that `traverse` is the same as `map >> sequence`. See also [Option.sequenceAsyncResult](sequenceAsyncResult.md).
+
+See also Scott Wlaschin's [Understanding traverse and sequence](https://fsharpforfunandprofit.com/posts/elevated-world-4/).
+
+## Examples
+
+### Example 1
+
+Say we have a function to get a number from a database (asynchronously), and multiply our input by that number if it's found:
+
+```fsharp
+let tryMultiplyWithDatabaseValue: float -> Async<Result<float, string>> = // ...
+```
+
+If we start with an optional vaue, then we could map this funciton using `Option.traverseAsyncResult` as follows:
+
+```fsharp
+let input = Some 1.234
+
+input // float option
+|> Option.traverseAsyncResult tryMultiplyWithDatabaseValue // Async<Result<float option, string>>
+```
+
+If we combine this with the [AsyncResult computation expression](../asyncResult/ce.md), we could directly `let!` the output:
+
+```fsharp
+asyncResult {
+    let input = Some 1.234
+
+    let! output = // float option
+        input // float option
+        |> Option.traverseAsyncResult tryMultiplyWithDatabaseValue // Async<Result<float option, string>>
+}
+```

src/FsToolkit.ErrorHandling/Option.fs

@@ -350,11 +350,13 @@ module Option =
         sequenceAsync ((map f) opt)
 
     /// <summary>
-    /// Converts a Option<Async<Result<'ok,'error>>> to an Async<Result<Option<'ok>,'error>>
+    /// Converts a Async<Result<'ok,'error>> option to an Async<Result<'ok option,'error>>
+    ///
+    /// Documentation is found here: <href>https://demystifyfp.gitbook.io/fstoolkit-errorhandling/fstoolkit.errorhandling/option/sequenceasyncresult</href>
     /// </summary>
     let inline sequenceAsyncResult
-        (optAsyncResult: Option<Async<Result<'T, 'E>>>)
-        : Async<Result<Option<'T>, 'E>> =
+        (optAsyncResult: Async<Result<'T, 'E>> option)
+        : Async<Result<'T option, 'E>> =
         async {
             match optAsyncResult with
             | Some asncRes ->
@@ -367,15 +369,17 @@ module Option =
         }
 
     /// <summary>
-    /// Maps an AsyncResult function over an Option, returning an AsyncResult Option.
+    /// Maps an AsyncResult function over an option, returning an AsyncResult option.
+    ///
+    /// /// Documentation is found here: <href>https://demystifyfp.gitbook.io/fstoolkit-errorhandling/fstoolkit.errorhandling/option/traverseasyncresult</href>
     /// </summary>
     /// <param name="f">The function to map over the Option.</param>
     /// <param name="opt">The Option to map over.</param>
     /// <returns>An AsyncResult Option with the mapped value.</returns>
     let inline traverseAsyncResult
         ([<InlineIfLambda>] f: 'T -> Async<Result<'U, 'E>>)
-        (opt: Option<'T>)
-        : Async<Result<Option<'U>, 'E>> =
+        (opt: 'T option)
+        : Async<Result<'U option, 'E>> =
         sequenceAsyncResult ((map f) opt)
 
     /// <summary>