This book serves three overlapping audiences:

• People who'd like to learn functional programming because they want to be ready if such languages become part of the mainstream.
• People who'll be working in an object-oriented language but want to use some functional programming idioms and tricks of the trade in their projects.
• People with less specific goals, but who believe that learning languages that conceptualize problems and solutions in radically different ways will make them better programmers in general.

The book uses Clojure, a popular functional language that runs on the Java Virtual Machine. It contains many exercises and their solutions.

For more about what the book covers, see the sample PDF. It includes the Introduction, the first chapter, and the glossary.

The book is "feature complete", but there will be bug fixes and improvements to the explanations over the next few months.

Praise

"This book, written by Brian Marick, is important. Indeed, it may be necessary. We need something to bridge the gap between the huge population of OO programmers, and the growing need for functional programmers. I’ve seen nothing else that fills this need so well."

— From a review by Robert "Uncle Bob" Martin

"@marick is blowing my mind with #fp_oo, building OO on top of FP."

— Larry Staton Jr.

"I have an understanding of monads for the first time thanks to @marick and his awesome book"

— Dave Kincaid

"'Functional Programming for the OO Programmer' by @marick features the best introduction to Clojure I've read so far."

— Sebastian Benz

"Bought #fp_oo by @marick today. Chapter 1 is the best #clojure intro I have read"

— Adrian Mowat

Welcome to the totally awesome Happy Learn Haskell Tutorial series! It's an easy gradual method to learn functional programming together. It's totally free for you to read online (at http://www.happylearnhaskelltutorial.com), because everyone should be able to learn Haskell!

You will start from the absolute beginning, so you don't need to know any programming. On the other hand, if you've had some frustrations with it in the past, then this way of explaining might be just for you!

By buying one or more copies, and telling all your friends about it, you will support us in building more volumes (we have big plans, which we'd love to be able to do).

Why will this series be easier and better to learn with than others?

1. Tackling reading first, and slowly introducing writing when enough examples have been seen to increase confidence, because reading & writing are separate skills
2. Many small, fun examples for each thing to keep interest: fun examples helps with motivation
3. Gradual, partial introduction of topics, in context: graded, less to take in at once
4. Not so much theory introduced before the practical has been introduced (same as examples) which gives a context for the theory
5. Pictures. Some of these are visual aides, which are useful as explanations: a picture tells 1000 words
6. No assumption of previous programming experience. Almost every other guide available assume some programming
7. Smaller sections because completing small things gives a real sense of achievement, which increases motivation
8. Tackling how to deconstruct problems using both top down and bottom up approaches: most guides don't tackle this in a simple or basics-first way
9. It's free to read and online, so able to be discussed in public - some guides are, others aren't
10. Not so math focussed including "mathy jargon". We keep away from "frightening" terms like catamorphism, lambda calculus, monad, etc. and these are only introduced when appropriate amounts of knowledge are present through repeated exposure to examples, so that it's obvious what is meant