How .NET Standard relates to .NET Platforms (in F#)

netstandard.fs

// Converted to F# from https://gist.github.com/davidfowl/8939f305567e1755412d6dc0b8baf1b7
module Analogy =
    type ASetOfApis = unit -> unit

    // Each interface represents a target framework and methods represents groups of APIs available on that target framework. 
    // The goal is to show the relationship between .NET Standard API surface and other .NET platforms

    // .NET Standard

    type INetStandard10 =
        abstract member Primatives  : ASetOfApis
        abstract member Reflection  : ASetOfApis
        abstract member Tasks       : ASetOfApis
        abstract member Collections : ASetOfApis
        abstract member Linq        : ASetOfApis

    type INetStandard11 =
        inherit INetStandard10
        abstract member ConcurrentCollections   : ASetOfApis
        abstract member InteropServices         : ASetOfApis

    type INetStandard12 =
        inherit INetStandard11
        abstract member ThreadingTimer : ASetOfApis

    type INetStandard13 =
        inherit INetStandard12
        abstract member FileSystem  : ASetOfApis
        abstract member Console     : ASetOfApis
        abstract member ThreadPool  : ASetOfApis
        abstract member Process     : ASetOfApis
        abstract member Sockets     : ASetOfApis
        abstract member AsyncLocal  : ASetOfApis  
    
    type INetStandard14 =
        inherit INetStandard13
        abstract member IsolatedStorage : ASetOfApis

    type INetStandard15 =
        inherit INetStandard14
        abstract member AssemblyLoadContext : ASetOfApis

    // .NET Framework 

    type INetFramework45 =
        inherit INetStandard11
        abstract member FileSystem  : ASetOfApis
        abstract member Console     : ASetOfApis
        abstract member ThreadPool  : ASetOfApis
        abstract member Crypto      : ASetOfApis
        abstract member WebSockets  : ASetOfApis
        abstract member Process     : ASetOfApis
        abstract member Sockets     : ASetOfApis
        
        abstract member AppDomain   : ASetOfApis
        abstract member Xml         : ASetOfApis
        abstract member Drawing     : ASetOfApis
        abstract member SystemWeb   : ASetOfApis
        abstract member WPF         : ASetOfApis
        abstract member WindowsForms: ASetOfApis
        abstract member WCF         : ASetOfApis
    
    type INetFramework451 =
        inherit INetFramework45
        inherit INetStandard12
        // TODO: .NET Framework 4.5.1 specific APIs

    type INetFramework452 =
        inherit INetFramework451
        inherit INetStandard12
        // TODO: .NET Framework 4.5.2 specific APIs

    type INetFramework46 =
        inherit INetFramework452
        inherit INetStandard13
        // TODO: .NET Framework 4.6 specific APIs

    type INetFramework461 =
        inherit INetFramework46
        inherit INetStandard14
        // TODO: .NET Framework 4.6.1 specific APIs

    type INetFramework462 =
        inherit INetFramework461
        inherit INetStandard15
        // TODO: .NET Framework 4.6 specific APIs
    
    // Mono
    
    type IMono43 =
        inherit INetFramework46
        abstract member MonoSpecificApi : ASetOfApis

    // Windows Universal Platform

    type IWindowsUniversalPlatform =
        inherit INetStandard14
        abstract member GPS     : ASetOfApis
        abstract member Xaml    : ASetOfApis 

    // Xamarin 

    type IXamarinIOS =
        inherit INetStandard15
        abstract member AppleAPIs : ASetOfApis

    type IXamarinAndroid =
        inherit INetStandard15
        abstract member GoogleAPIs : ASetOfApis

    // .NET Core

    type INetCoreApp10 =
        inherit INetStandard15

    // Future platform

    type ISomeFuturePlatform = 
        inherit INetStandard13
        // A future platform chooses to implement a specific .NET Standard version.
        // All libraries that target that version are instantly compatible with this new
        // platform

module Samples =
    open Analogy

    /// This example shows that a library that needs access to target .NET Standard 1.3
    /// can only access APIs available in that .NET Standard. Even though similar the APIs exist on .NET 
    /// Framework 4.5, it implements a version of .NET Standard that isn't compatible with the library.
    /// </summary>
    type Example1 () =
        member this.Net45Application (platform : #INetFramework45) =
            // .NET Framework 4.5 has access to all .NET Framework APIs
            platform.FileSystem()
            platform.Console()

            // This fails because .NET Framework 4.5 does not implement .NET Standard 1.3
            // this.NetStandardLibrary13(platform)
            // error FS0001: The type 'INetFramework45' is not compatible with the type 'INetStandard13'
            
        member this.NetStandardLibrary13 (platform: #INetStandard13) =
            platform.FileSystem()
            platform.Console()

    /// This example shows a library targeting multiple frameworks and 2 different applications
    /// using that library. MultipleTargetsLibrary needs access to the FileSystem, that API was only available
    /// in .NET Standard 1.3. .NET Standard 1.3 only works with .NET Framework 4.6. Because of this
    /// MultipleTargetsLibrary needs to add support for .NET Framework 4.5 explicitly.
    type Example2() =
        // On the .NET Core 1.0 application, the INetStandard13 implementation is choson
        member this.Net45Application (platform: #INetFramework451) = platform.FileSystem()
        member this.NetCoreApplication (platform: #INetCoreApp10) = platform.FileSystem()
        
    /// This example shows how future platforms can be added without the need to change libraries that
    /// target the .NET Standard. JSON.NET targets .NET Standard 1.0 and can run on *ANY* platform that
    /// implements the standard.
    type Example3 () =
        /// You are about to use JSON.NET on a future platform without recompiling it
        member this.FuturePlatformApplication (platform: #ISomeFuturePlatform) = this.JsonNet platform
        
        /// Represents an implementation of JSON.NET which supports .NET Standard 1.0
        member this.JsonNet (platform: #INetStandard10) =
            platform.Linq()
            platform.Reflection()
            platform.Collections()