+ singleton

Author: gusty

src/FSharp.Control.TaskSeq/TaskSeq.fs

@@ -15,6 +15,20 @@ module TaskSeq =
         for c: 'T in [] do
             yield c
     }
+    
+    let singleton (source: 'T) =
+        { new IAsyncEnumerable<'T> with
+            member _.GetAsyncEnumerator(_) =
+                let mutable started = false
+                { new IAsyncEnumerator<'T> with
+                    member _.MoveNextAsync () =
+                        let r = ValueTask.FromResult (not started)
+                        started <- true
+                        r                        
+                    member _.get_Current () : 'T = if started then source else invalidOp "Enumeration has not started. Call MoveNextAsync."
+                    member _.DisposeAsync () = ValueTask.CompletedTask
+                }
+        }
 
     let isEmpty source = Internal.isEmpty source