+ pmap2 and pmap3 to Async, Task and ValueTask

Author: gusty

src/FSharpPlus/Extensions/Async.fs

@@ -10,7 +10,7 @@ module Async =
     let map f x = async.Bind (x, async.Return << f)
 
     /// <summary>Creates an async workflow from two workflows 'x' and 'y', mapping its results with 'f'.</summary>
-    /// <remarks>Workflows are run in sequence.</remarks>
+    /// <remarks>Workflows are run in sequence, for parallel use pmap2.</remarks>
     /// <param name="f">The mapping function.</param>
     /// <param name="x">First async workflow.</param>
     /// <param name="y">Second async workflow.</param>
@@ -20,7 +20,7 @@ module Async =
         return f a b}
 
     /// <summary>Creates an async workflow from three workflows 'x', 'y' and 'z', mapping its results with 'f'.</summary>
-    /// <remarks>Workflows are run in sequence.</remarks>
+    /// <remarks>Workflows are run in sequence, for parallel use pmap3.</remarks>
     /// <param name="f">The mapping function.</param>
     /// <param name="x">First async workflow.</param>
     /// <param name="y">Second async workflow.</param>
@@ -31,6 +31,43 @@ module Async =
         let! c = z
         return f a b c}
 
+    /// <summary>Creates an async workflow from two workflows 'x' and 'y', mapping its results with 'f'.</summary>
+    /// <remarks>Similar to map2 but workflows are run in parallel.</remarks>
+    /// <param name="f">The mapping function.</param>
+    /// <param name="x">First async workflow.</param>
+    /// <param name="y">Second async workflow.</param>
+    #if FABLE_COMPILER
+    let pmap2 f x y = map2 f x y
+    #else
+    let pmap2 f x y = async {
+        let! ct = Async.CancellationToken
+        let x = Async.StartImmediateAsTask (x, ct)
+        let y = Async.StartImmediateAsTask (y, ct)
+        let! x' = Async.AwaitTask x
+        let! y' = Async.AwaitTask y
+        return f x' y' }
+    #endif
+
+    /// <summary>Creates an async workflow from three workflows 'x', 'y' and 'z', mapping its results with 'f'.</summary>
+    /// <remarks>Similar to map3 but workflows are run in parallel.</remarks>
+    /// <param name="f">The mapping function.</param>
+    /// <param name="x">First async workflow.</param>
+    /// <param name="y">Second async workflow.</param>
+    /// <param name="z">third async workflow.</param>
+    #if FABLE_COMPILER
+    let pmap3 f x y z = map3 f x y z
+    #else
+    let pmap3 f x y z = async {
+        let! ct = Async.CancellationToken
+        let x = Async.StartImmediateAsTask (x, ct)
+        let y = Async.StartImmediateAsTask (y, ct)
+        let z = Async.StartImmediateAsTask (z, ct)
+        let! x' = Async.AwaitTask x
+        let! y' = Async.AwaitTask y
+        let! z' = Async.AwaitTask z
+        return f x' y' z' }
+    #endif
+
     /// <summary>Creates an async workflow from two workflows 'x' and 'y', tupling its results.</summary>
     let zip x y = async {
         let! a = x

src/FSharpPlus/Extensions/Task.fs

@@ -134,6 +134,28 @@ module Task =
                                 ) |> ignore) |> ignore) |> ignore
             tcs.Task
 
+    /// <summary>Creates a task workflow from two workflows 'x' and 'y', mapping its results with 'f'.</summary>
+    /// <remarks>Similar to map2 but workflows are run in parallel.</remarks>
+    /// <param name="f">The mapping function.</param>
+    /// <param name="x">First task workflow.</param>
+    /// <param name="y">Second task workflow.</param>
+    let pmap2 f x y = task {
+        let! x' = x
+        let! y' = y
+        return f x' y' }
+
+    /// <summary>Creates a task workflow from three workflows 'x', 'y' and z, mapping its results with 'f'.</summary>
+    /// <remarks>Similar to map2 but workflows are run in parallel.</remarks>
+    /// <param name="f">The mapping function.</param>
+    /// <param name="x">First task workflow.</param>
+    /// <param name="y">Second task workflow.</param>
+    /// <param name="z">Third task workflow.</param>
+    let pmap3 f x y z = task {
+        let! x' = x
+        let! y' = y
+        let! z' = z
+        return f x' y' z' }
+
     /// <summary>Creates a task workflow that is the result of applying the resulting function of a task workflow
     /// to the resulting value of another task workflow</summary>
     /// <param name="f">Task workflow returning a function</param>

src/FSharpPlus/Extensions/ValueTask.fs

@@ -62,6 +62,35 @@ module ValueTask =
                     with e -> tcs.SetException e)))
         tcs.Task |> ValueTask<'W>
 
+    /// <summary>Creates a task workflow from two workflows 'x' and 'y', mapping its results with 'f'.</summary>
+    /// <remarks>Similar to map2 but workflows are run in parallel.</remarks>
+    /// <param name="f">The mapping function.</param>
+    /// <param name="x">First ValueTask workflow.</param>
+    /// <param name="y">Second ValueTask workflow.</param>
+    /// <param name="z">Third ValueTask workflow.</param>
+    let pmap2 (f: 'T -> 'U -> 'V) (x: ValueTask<'T>) (y: ValueTask<'U>) : ValueTask<'V> =
+        task {
+            let! x' = x
+            let! y' = y
+            return f x' y'
+        }
+        |> ValueTask<'V>
+
+    /// <summary>Creates a ValueTask workflow from three workflows 'x', 'y' and z, mapping its results with 'f'.</summary>
+    /// <remarks>Similar to map3 but workflows are run in parallel.</remarks>
+    /// <param name="f">The mapping function.</param>
+    /// <param name="x">First ValueTask workflow.</param>
+    /// <param name="y">Second ValueTask workflow.</param>
+    /// <param name="z">Third ValueTask workflow.</param>
+    let pmap3 (f: 'T -> 'U -> 'V -> 'W) (x: ValueTask<'T>) (y: ValueTask<'U>) (z: ValueTask<'V>) : ValueTask<'W> =
+        task {
+            let! x' = x
+            let! y' = y
+            let! z' = z
+            return f x' y' z'
+        }
+        |> ValueTask<'W>
+
     /// <summary>Creates a ValueTask workflow that is the result of applying the resulting function of a ValueTask workflow
     /// to the resulting value of another ValueTask workflow</summary>
     /// <param name="f">ValueTask workflow returning a function</param>