Functional Programming for the Object-Oriented Programmer

Many, many of the legendary programmers know many programming languages. What they know from one language helps them write better code in another one. But it’s not really the language that matters: adding knowledge of C# to your knowledge of Java doesn’t make you much better. The languages are too similar: they encourage you to look at problems in pretty much the same way. You need to know languages that conceptualize problems and solutions in substantially different ways.

Once upon a time, object-oriented programming was a radical departure from what most programmers knew. So learning it was both hard and mind-expanding. Nowadays, the OO style (or some approximation to it) is the dominant one, so ambitious people need to seek out different styles.

The functional programming style is nicely different from the OO style, but there are many interesting points of comparison between them. This book aims to teach you key elements of the functional style, helping you take them back to your OO language.

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.