This book is the first publication in Russia that examines functional programming in full, sufficient for a beginner to understand and for the book to be used as a reference tool for those who already use the functional programming paradigm in their practice. The study of applied fundamentals is shown using the example of the Haskell language, which today is the most powerful and developed tool for functional programming. The publication can be used both as a textbook on functional programming and as an independent textbook in related disciplines, primarily in combinatorial logic and λ - calculus. The book will also be of interest to those who are seriously engaged in the study of new computer technologies, artificial intelligence and expert systems. The book comes with a CD with a Haskell translator, as well as various libraries for it, additional utilities and working examples of programs discussed in the book .