Flop is a general purpose library that helps writing C# programs in functional style. It offers various features commonly found in functional languages, such as immutable data structures, parser combinators, and property based testing. When using Flop your programs resemble more code written in F# or Haskell than idiomatic, imperative C#. The goal of the library is to make C# programs more succinct and powerful using the principles of functional programming. The benefits of functional paradigm, such as easier reasoning about program correctness and better support for concurrency, become more achievable with the help of the library.