list isEmpty if and only if length is 0

dotnet · Jul 29, 2015 · 14abd70 · 14abd70
1 parent 6020bea
commit 14abd70
Showing 1 changed file with 12 additions and 0 deletions.
diff --git a/src/fsharp/FSharp.Core.PropertyTests/ListProperties.fs b/src/fsharp/FSharp.Core.PropertyTests/ListProperties.fs
@@ -148,6 +148,18 @@ let ``head fails when list isEmpty`` () =
     Check.QuickThrowOnFailure head_and_isEmpty<string>
     Check.QuickThrowOnFailure head_and_isEmpty<NormalFloat>
 
+let length_and_isEmpty<'a when 'a : comparison>  (xs : list<'a>) =
+    let a = List.length xs = 0
+    let b = List.isEmpty xs
+
+    a = b
+
+[<Test>]
+let ``list isEmpty if and only if length is 0`` () =   
+    Check.QuickThrowOnFailure length_and_isEmpty<int>
+    Check.QuickThrowOnFailure length_and_isEmpty<string>
+    Check.QuickThrowOnFailure length_and_isEmpty<NormalFloat>
+
 let findBack_and_exists<'a when 'a : comparison>  (xs : list<'a>) f =
     let a = 
         try