Merge pull request #87 from Karamell/truncate

Add truncate as an alias to mimic Seq.

src/FSharp.Control.AsyncSeq/AsyncSeq.fs

@@ -1285,6 +1285,8 @@ module AsyncSeq =
                   let! moven = ie.MoveNext()
                   b := moven
               else b := None }
+
+  let truncate count source = take count source
 
   let skip count (source : AsyncSeq<'T>) : AsyncSeq<_> = asyncSeq {
       if (count < 0) then invalidArg "count" "must be non-negative"

src/FSharp.Control.AsyncSeq/AsyncSeq.fsi

@@ -397,8 +397,12 @@ module AsyncSeq =
     val skipWhile : predicate:('T -> bool) -> source:AsyncSeq<'T> -> AsyncSeq<'T>
 
     /// Returns the first N elements of an asynchronous sequence
+    /// does not cast an exception if count is larger than the sequence length.
     val take : count:int -> source:AsyncSeq<'T> -> AsyncSeq<'T>
 
+    /// Alias for take
+    val truncate : count:int -> source:AsyncSeq<'T> -> AsyncSeq<'T>
+
     /// Skips the first N elements of an asynchronous sequence and
     /// then returns the rest of the sequence unmodified.
     val skip : count:int -> source:AsyncSeq<'T> -> AsyncSeq<'T>

tests/FSharp.Control.AsyncSeq.Tests/AsyncSeqTests.fs

@@ -1401,6 +1401,16 @@ let ``AsyncSeq.take should work``() =
   let ls = ss |> AsyncSeq.toList
   ()
 
+[<Test>]
+let ``AsyncSeq.truncate should work like take``() =  
+  let s = asyncSeq {
+    yield ["a",1] |> Map.ofList
+  }
+  let expected = s |> AsyncSeq.take 1
+  let actual =  s |> AsyncSeq.truncate 1
+  Assert.AreEqual(expected, actual)
+
+
 [<Test>]
 let ``AsyncSeq.mapAsyncParallel should maintain order`` () =
   for i in 0..100 do