+ Tuple2 and Tuple3 extensions

src/FSharpPlus/Data/State.fs

@@ -20,7 +20,7 @@ module State =
     let map   f (State m) = State (fun s -> let (a: 'T, s') = m s in (f a, s'))                                   : State<'S,'U>
 
     /// Combines two States into one by applying a mapping function.
-    let map2 (f: 'T->'U->_) (State x) (State y) = State (fun s -> let (g, s1) = mapItem1 f (x s) in mapItem1 g (y s1))  : State<'S,'V>
+    let map2 (f: 'T->'U->_) (State x) (State y) = State (fun s -> let (g, s1) = Tuple2.mapItem1 f (x s) in Tuple2.mapItem1 g (y s1)) : State<'S,'V>
 
     let bind  f (State m) = State (fun s -> let (a: 'T, s') = m s in run (f a) s')                                : State<'S,'U>
     let apply (State f) (State x) = State (fun s -> let (f', s1) = f s in let (x': 'T, s2) = x s1 in (f' x', s2)) : State<'S,'U>

src/FSharpPlus/Extensions/Tuple.fs

@@ -0,0 +1,14 @@
+namespace FSharpPlus
+
+/// Additional operations on Tuple (,)
+[<RequireQualifiedAccess>]
+module Tuple2 =
+    let mapItem1 f (x, y) = (f x, y)
+    let mapItem2 f (x, y) = (x, f y)
+
+/// Additional operations on Tuple (,,)
+[<RequireQualifiedAccess>]
+module Tuple3 =
+    let mapItem1 f (x, y, z) = (f x, y, z)
+    let mapItem2 f (x, y, z) = (x, f y, z)
+    let mapItem3 f (x, y, z) = (x, y, f z)

src/FSharpPlus/FSharpPlus.fsproj

@@ -29,7 +29,7 @@
     <!--<OutputPath>..\..\bin</OutputPath>-->
   </PropertyGroup>
   <ItemGroup>
-    <Compile Include="Internals.fs" />    
+    <Compile Include="Internals.fs" />
     <Compile Include="Extensions/Option.fs" />
     <Compile Include="Extensions/Nullable.fs" />
     <Compile Include="Extensions/Result.fs" />
@@ -51,6 +51,7 @@
     <Compile Include="Extensions/Task.fs" />
     <Compile Include="Extensions/Async.fs" />
     <Compile Include="Extensions/Extensions.fs" />
+    <Compile Include="Extensions/Tuple.fs" />
     <Compile Include="TypeLevel/TypeLevelOperators.fs" />
     <Compile Include="TypeLevel/TypeBool.fs" />
     <Compile Include="TypeLevel/TypeNat.fs" />