This repo contains the code samples, exercises and solutions for the book Functional Programming in C#, 2nd Edition published by Manning. The 2nd Edition builds on the success of the 1st, but has been updated to reflect new features in C# 10 and .NET 6.

The code samples are organized in the following projects:

• Examples: examples used throughout the book, by chapter
• Exercises: placeholders for you to do the exercises, compile and run them; and compare to the provided solutions
• LaYumba.Functional: a functional library that we develop throughout the book
• LaYumba.Functional.Data: very simple functional data structures discussed in Chapter 12
• LaYumba.Functional.Tests: also illustrative of topics explained in the book, and useful to better understand the constructs in the library

Note: you are welcome to reference LaYumba.Functional from your projects via NuGet, and submit PRs with improvements, but the main intent of this library is pedagogical. For a more fully-fledged functional library, consider LanguageExt

The code samples use .NET 6, and should compile and run on all major OS's via the dotnet CLI.

• .NET Core 6 SDK

To check this is available, type dotnet --version at the command prompt, and you should get 6.0 or greater

$ git clone git@github.com:la-yumba/functional-csharp-code-2.git
$ cd functional-csharp-code-2
$ dotnet build

Use the dotnet test command, for example:

$ cd LaYumba.Functional.Tests
$ dotnet test

tests in the Exercises and Examples projects can be run in the same way.

Many code samples in the book can be run, in case you'd like to debug or "see that it works". The pattern is:

$ cd Examples
$ dotnet run Greetings

Throughout the book, I encourage readers to try things out in the REPL.

• If you use Visual Studio, you can start the REPL by going to View > Other Windows > C# Interactive (short tutorial here)
• On Mono, use the csharp or csi command
• There are several other REPLs available, some even run in the browser

You'll often need to import LaYumba.Functional in the REPL. In C# Interactive, this can be done like so:

#r "functional-csharp-code-2\LaYumba.Functional\bin\Debug\net6.0\LaYumba.Functional.dll"

The path above may not work for you, in which case use an absolute path to the dll, or type Directory.GetCurrentDirectory() into the REPL to see what to use as a base for a relative path.

Next, add these imports:

using LaYumba.Functional;
using static LaYumba.Functional.F;

You're now ready to experiment with functional code right in the REPL, for example:

> var plus = (int a, int b) => a + b;
> Some(plus).Apply(1).Apply(2)
[Some(3)]
> Some(plus).Apply(1).Apply(None)
[None]

• edit the code in Exercises as needed

• edit Exercises/Program.cs to start the class you want

• run it with:

  $ cd Exercises
  $ dotnet run
  

• run your tests:

  $ cd Exercises
  $ dotnet test