From 9de8799d57eea9b0d9d67d0810b01e5b236aaaaf Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Sat, 20 Jun 2020 01:25:55 +0200
Subject: [PATCH 1/6] Turn String.replicate from O(n) into O(log(n))
---
src/fsharp/FSharp.Core/string.fs | 24 +++++++++++++++++++-----
1 file changed, 19 insertions(+), 5 deletions(-)
diff --git a/src/fsharp/FSharp.Core/string.fs b/src/fsharp/FSharp.Core/string.fs
index 7e4b65f1a08..e973739f1e7 100644
--- a/src/fsharp/FSharp.Core/string.fs
+++ b/src/fsharp/FSharp.Core/string.fs
@@ -81,13 +81,27 @@ namespace Microsoft.FSharp.Core
let replicate (count:int) (str:string) =
if count < 0 then invalidArgInputMustBeNonNegative "count" count
- if String.IsNullOrEmpty str then
+ let len = length str
+ if len = 0 || count = 0 then
String.Empty
else
- let res = StringBuilder(count * str.Length)
- for i = 0 to count - 1 do
- res.Append str |> ignore
- res.ToString()
+ // Using the primitive, because array.fs is not yet in scope. It's safe: both len and count are positive.
+ let target = Microsoft.FSharp.Primitives.Basics.Array.zeroCreateUnchecked (len * count)
+ let source = str.ToCharArray()
+
+ // O(log(n)) performance loop:
+ // Copy first string, then keep copying what we already copied
+ // (i.e., doubling it) until we reach or pass the halfway point
+ Array.Copy(source, 0, target, 0, len)
+ let mutable i = len
+ while i * 2 < target.Length do
+ Array.Copy(target, 0, target, i, i)
+ i <- i * 2
+
+ // finally, copy the remain half, or less-then half
+ Array.Copy(target, 0, target, i, target.Length - i)
+ new String(target)
+
[<CompiledName("ForAll")>]
let forall predicate (str:string) =
From 739fe306999842817a8ce37bbf43449f3ab825c6 Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Sat, 20 Jun 2020 01:40:37 +0200
Subject: [PATCH 2/6] Cleanup String.replicate tests by removing usages of
"foo"
---
.../Microsoft.FSharp.Collections/StringModule.fs | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs b/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
index a72ab64e236..4bf4a0f5a40 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
@@ -125,11 +125,11 @@ type StringModule() =
[<Test>]
member this.Replicate() =
- let e1 = String.replicate 0 "foo"
+ let e1 = String.replicate 0 "Snickersnee"
Assert.AreEqual("", e1)
- let e2 = String.replicate 2 "foo"
- Assert.AreEqual("foofoo", e2)
+ let e2 = String.replicate 2 "Collywobbles, "
+ Assert.AreEqual("Collywobbles, Collywobbles, ", e2)
let e3 = String.replicate 2 null
Assert.AreEqual("", e3)
From 9fdd9209600a2a17224c778e517af04b40be0f9c Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Sat, 20 Jun 2020 01:42:27 +0200
Subject: [PATCH 3/6] String.replicate: add tests for missing cases, and for
the new O(log(n)) cut-off points
---
.../StringModule.fs | 17 ++++++++++++++++-
1 file changed, 16 insertions(+), 1 deletion(-)
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs b/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
index 4bf4a0f5a40..e3bea8a7c18 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
@@ -1,4 +1,4 @@
-// Copyright (c) Microsoft Corporation. All Rights Reserved. See License.txt in the project root for license information.
+// Copyright (c) Microsoft Corporation. All Rights Reserved. See License.txt in the project root for license information.
namespace FSharp.Core.UnitTests.Collections
@@ -134,6 +134,21 @@ type StringModule() =
let e3 = String.replicate 2 null
Assert.AreEqual("", e3)
+ let e4 = String.replicate 300_000 ""
+ Assert.AreEqual("", e4)
+
+ let e5 = String.replicate 23 "天地玄黃，宇宙洪荒。"
+ Assert.AreEqual(230 , e5.Length)
+ Assert.AreEqual("天地玄黃，宇宙洪荒。天地玄黃，宇宙洪荒。", e5.Substring(0, 20))
+
+ // this tests the cut-off point for the O(log(n)) algorithm by using a prime number
+ let e6 = String.replicate 84673 "!!!"
+ Assert.AreEqual(84673 * 3, e6.Length)
+
+ // this tests the cut-off point for the O(log(n)) algorithm by using a 2^x number
+ let e6 = String.replicate 1024 "!!!"
+ Assert.AreEqual(1024 * 3, e6.Length)
+
CheckThrowsArgumentException(fun () -> String.replicate -1 "foo" |> ignore)
[<Test>]
From 02abc25636ae3c4b1bd2c0050faedd4d4c65169c Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Sat, 20 Jun 2020 02:59:44 +0200
Subject: [PATCH 4/6] Improve String.replicate algorithm further
---
src/fsharp/FSharp.Core/string.fs | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/src/fsharp/FSharp.Core/string.fs b/src/fsharp/FSharp.Core/string.fs
index e973739f1e7..c853a778432 100644
--- a/src/fsharp/FSharp.Core/string.fs
+++ b/src/fsharp/FSharp.Core/string.fs
@@ -79,11 +79,22 @@ namespace Microsoft.FSharp.Core
[<CompiledName("Replicate")>]
let replicate (count:int) (str:string) =
- if count < 0 then invalidArgInputMustBeNonNegative "count" count
+ //if count < 0 then invalidArgInputMustBeNonNegative "count" count
let len = length str
if len = 0 || count = 0 then
String.Empty
+
+ elif len = 1 then
+ new String(str.[0], count)
+
+ elif count <= 4 then
+ match count with
+ | 1 -> str
+ | 2 -> String.Concat(str, str)
+ | 3 -> String.Concat(str, str, str)
+ | _ -> String.Concat(str, str, str, str)
+
else
// Using the primitive, because array.fs is not yet in scope. It's safe: both len and count are positive.
let target = Microsoft.FSharp.Primitives.Basics.Array.zeroCreateUnchecked (len * count)
From d7f738711506b5d719d05e0efdaf3fa767ce68ac Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Sat, 20 Jun 2020 03:11:24 +0200
Subject: [PATCH 5/6] Add tests for String.replicate covering all
lines/branches of algo
---
.../StringModule.fs | 20 +++++++++++++++----
1 file changed, 16 insertions(+), 4 deletions(-)
diff --git a/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs b/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
index e3bea8a7c18..aa486fddd6a 100644
--- a/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
+++ b/tests/FSharp.Core.UnitTests/FSharp.Core/Microsoft.FSharp.Collections/StringModule.fs
@@ -141,13 +141,25 @@ type StringModule() =
Assert.AreEqual(230 , e5.Length)
Assert.AreEqual("天地玄黃，宇宙洪荒。天地玄黃，宇宙洪荒。", e5.Substring(0, 20))
- // this tests the cut-off point for the O(log(n)) algorithm by using a prime number
+ // This tests the cut-off point for the O(log(n)) algorithm with a prime number
let e6 = String.replicate 84673 "!!!"
Assert.AreEqual(84673 * 3, e6.Length)
- // this tests the cut-off point for the O(log(n)) algorithm by using a 2^x number
- let e6 = String.replicate 1024 "!!!"
- Assert.AreEqual(1024 * 3, e6.Length)
+ // This tests the cut-off point for the O(log(n)) algorithm with a 2^x number
+ let e7 = String.replicate 1024 "!!!"
+ Assert.AreEqual(1024 * 3, e7.Length)
+
+ let e8 = String.replicate 1 "What a wonderful world"
+ Assert.AreEqual("What a wonderful world", e8)
+
+ let e9 = String.replicate 3 "أضعت طريقي! أضعت طريقي" // means: I'm lost
+ Assert.AreEqual("أضعت طريقي! أضعت طريقيأضعت طريقي! أضعت طريقيأضعت طريقي! أضعت طريقي", e9)
+
+ let e10 = String.replicate 4 "㏖ ㏗ ℵ "
+ Assert.AreEqual("㏖ ㏗ ℵ ㏖ ㏗ ℵ ㏖ ㏗ ℵ ㏖ ㏗ ℵ ", e10)
+
+ let e11 = String.replicate 5 "5"
+ Assert.AreEqual("55555", e11)
CheckThrowsArgumentException(fun () -> String.replicate -1 "foo" |> ignore)
From 4f60f0b0d19571e8f4e05d2a4588da98f82faab9 Mon Sep 17 00:00:00 2001
From: Abel Braaksma <abel.online@xs4all.nl>
Date: Sat, 20 Jun 2020 03:15:04 +0200
Subject: [PATCH 6/6] Fix accidental comment
---
src/fsharp/FSharp.Core/string.fs | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/fsharp/FSharp.Core/string.fs b/src/fsharp/FSharp.Core/string.fs
index c853a778432..32e48bd7a6b 100644
--- a/src/fsharp/FSharp.Core/string.fs
+++ b/src/fsharp/FSharp.Core/string.fs
@@ -79,7 +79,7 @@ namespace Microsoft.FSharp.Core
[<CompiledName("Replicate")>]
let replicate (count:int) (str:string) =
- //if count < 0 then invalidArgInputMustBeNonNegative "count" count
+ if count < 0 then invalidArgInputMustBeNonNegative "count" count
let len = length str
if len = 0 || count = 0 then