Lazy

F#/Lazy.Test/Lazy.Test.fsproj

@@ -0,0 +1,29 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+
+    <IsPackable>false</IsPackable>
+    <GenerateProgramFile>true</GenerateProgramFile>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="LazyTest.fs" />
+
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
+    <PackageReference Include="FsUnit" Version="6.0.0" />
+    <PackageReference Include="NUnit" Version="4.1.0" />
+    <PackageReference Include="NUnit.Analyzers" Version="3.9.0" />
+    <PackageReference Include="NUnit3TestAdapter" Version="4.5.0" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\Lazy\Lazy.fsproj" />
+  </ItemGroup>
+
+</Project>

F#/Lazy.Test/LazyTest.fs

@@ -0,0 +1,67 @@
+module Lazy.Test
+
+open NUnit.Framework
+open FsUnit
+
+type Counter () =
+    let mutable callCounter = 0
+    member this.Increment () = 
+        System.Threading.Interlocked.Increment(&callCounter)
+    member this.Counter = callCounter
+
+let lazyImplementations =  
+    [ 
+    (fun func -> S.Lazy<int> func :> ILazy.ILazy<int>) 
+    (fun func -> M.Lazy func)
+    (fun func -> LF.Lazy func)
+    ] |> List.map (fun x -> TestCaseData(x))
+
+[<Test>]
+[<TestCaseSource("lazyImplementations")>]
+let getTest (genLazy) =
+    let l : ILazy.ILazy<int> = genLazy (fun () -> 1)
+    l.Get() |> should equal 1
+
+[<Test>]
+let singleThreadCountTest () =
+    let counter = Counter()
+    let l : ILazy.ILazy<int> = S.Lazy<int>(counter.Increment)
+    l.Get() |> ignore
+    l.Get() |> ignore
+    l.Get() |> ignore
+    counter.Counter |> should equal 1
+
+[<Test>]
+let simpleMultiThrCountTest () =
+    let counter = Counter()
+    let l : ILazy.ILazy<int> = M.Lazy<int>(counter.Increment)
+    l.Get() |> ignore
+    l.Get() |> ignore
+    l.Get() |> ignore
+    counter.Counter |> should equal 1
+
+[<Test>]
+let complexMultiThrCountTest () =
+    let counter = Counter()
+    let l : ILazy.ILazy<int> = M.Lazy<int>(counter.Increment)
+    let getTask = task { return l.Get() }
+    let results = (fun _ -> getTask |> Async.AwaitTask) |> Seq.initInfinite  |> Seq.take 10 |> Async.Parallel |> Async.RunSynchronously
+    counter.Counter |> should equal 1
+    Seq.iter (fun x -> (x = (Seq.last results)) |> should equal true) results
+
+[<Test>]
+let simpleLockFreeTest () =
+    let counter = Counter()
+    let l : ILazy.ILazy<int> = LF.Lazy<int>(counter.Increment)
+    l.Get() |> ignore
+    l.Get() |> ignore
+    l.Get() |> ignore
+    counter.Counter |> should equal 1
+
+[<Test>]
+let complexLockFreeTest () =
+    let counter = Counter()
+    let l : ILazy.ILazy<int> = LF.Lazy<int>(counter.Increment)
+    let getTask = task { return l.Get() }
+    let results = (fun _ -> getTask |> Async.AwaitTask) |> Seq.initInfinite  |> Seq.take 10 |> Async.Parallel |> Async.RunSynchronously
+    Seq.iter (fun x -> (x = (Seq.last results)) |> should equal true) results

F#/Lazy/ILazy.fs

@@ -0,0 +1,12 @@
+module Lazy.ILazy
+
+/// <summary>
+/// Interface for lazy function calculation
+/// </summary>
+/// <typeparam name="'a">Function return value</typeparam>
+type ILazy<'a> =
+    /// <summary>
+    /// Lazily calculates given function
+    /// </summary>
+    /// <returns>Function result</returns>
+    abstract member Get: unit -> 'a

F#/Lazy/Lazy.fsproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <GenerateDocumentationFile>true</GenerateDocumentationFile>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="ILazy.fs" />
+    <Compile Include="SingleThreadedLazy.fs" />
+    <Compile Include="MultiThreadedLazy.fs" />
+    <Compile Include="LockFreeLazy.fs" />
+  </ItemGroup>
+
+</Project>

F#/Lazy/LockFreeLazy.fs

@@ -0,0 +1,14 @@
+module Lazy.LF
+
+/// <summary>
+/// Lock free multi threaded implementation of iLazy interface
+/// </summary>
+/// <typeparam name="'a">Result type</typeparam>
+type Lazy<'a>(func)  = 
+    let mutable value : Option<'a> = None
+    interface ILazy.ILazy<'a> with
+        member this.Get() =
+            if value.IsNone then
+                let localValue = func()
+                System.Threading.Interlocked.CompareExchange(&value, Some(localValue), None) |> ignore
+            value.Value

F#/Lazy/MultiThreadedLazy.fs

@@ -0,0 +1,17 @@
+module Lazy.M
+
+/// <summary>
+/// Multi threaded implementation of iLazy interface
+/// </summary>
+/// <typeparam name="'a">Result type</typeparam>
+type Lazy<'a>(func)  = 
+    let mutable value : Option<'a> = None
+    let valueLock = obj
+    interface ILazy.ILazy<'a> with
+        member this.Get() =
+            if value.IsNone then
+                lock valueLock (fun () ->
+                    if value.IsNone then
+                        value <- Some(func())
+                )
+            value.Value

F#/Lazy/SingleThreadedLazy.fs

@@ -0,0 +1,13 @@
+module Lazy.S
+
+/// <summary>
+/// Single threaded implementation of iLazy interface
+/// </summary>
+/// <typeparam name="'a">Result type</typeparam>
+type Lazy<'a>(f)  = 
+    let mutable value : Option<'a> = None
+    interface ILazy.ILazy<'a> with
+        member this.Get() =
+            if value.IsNone then
+                value <- Some(f())
+            value.Value

F#/forSpbu.sln

@@ -21,6 +21,10 @@ Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "07.03", "07.03", "{5CA9053B
 EndProject
 Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Homework1", "Homework1\Homework1.fsproj", "{04B15EE4-079A-42ED-ACC8-E2DCD25281C6}"
 EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Lazy", "Lazy\Lazy.fsproj", "{31761996-9105-4FCD-A2BE-87F64952A72A}"
+EndProject
+Project("{F2A71F9B-5D33-465A-A702-920D77279786}") = "Lazy.Test", "Lazy.Test\Lazy.Test.fsproj", "{F290B1F9-5753-4585-881D-25641368A803}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -58,6 +62,14 @@ Global
 		{89A935E8-B5F3-435D-ACC3-A99DD7C66178}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{89A935E8-B5F3-435D-ACC3-A99DD7C66178}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{89A935E8-B5F3-435D-ACC3-A99DD7C66178}.Release|Any CPU.Build.0 = Release|Any CPU
+		{31761996-9105-4FCD-A2BE-87F64952A72A}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{31761996-9105-4FCD-A2BE-87F64952A72A}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{31761996-9105-4FCD-A2BE-87F64952A72A}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{31761996-9105-4FCD-A2BE-87F64952A72A}.Release|Any CPU.Build.0 = Release|Any CPU
+		{F290B1F9-5753-4585-881D-25641368A803}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{F290B1F9-5753-4585-881D-25641368A803}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{F290B1F9-5753-4585-881D-25641368A803}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{F290B1F9-5753-4585-881D-25641368A803}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(NestedProjects) = preSolution
 		{7937CDA8-8285-4E23-AD1A-FC0F04FEEFE6} = {91E3BDA2-0836-46C2-95F0-02513FD7F13F}