Since Java 8 so called lambda expressions can be used by Java developers. But what does it mean… Lambda? The talk will be about story behind this term, from a little bit more scientific point of view. Church Lambda calculus, Entscheidungsproblem and incompleteness theorem. Almost all of that will be presented in Java – in the language that you understand. And of course you can later impress your friends with some impressive math tricks. There are going to be shown some very crazy code pieces such as perfectly unusable implementation of boolean (based on lambda expressions). Come and see what purely functional really means.