This is a book for programmers who want to understand their own craft better.

Let's face it: if you write software for a living, it's likely you spent most of your career working on boring business apps, which means lots and lots of straightforward code. You use compilers and interpreters all day long, but can't begin to imagine how they work on the inside. The very tools you rely on are black boxes, if not outright dark magic. Oh, they do teach this stuff in college, but even people who went there (I didn't) often run away from the dreaded compiler course.

And that's all a shame. Making your own programming language is actually very easy and fun. Many people do it as a hobby. (Decades of academic research have paid off big time.) It's teaching others how to do it that seems to be a problem still.

There are many books on this topic. Mine has two goals:

• to explain things in plain English, for any programmer, even beginners;
• to yield a useful interpreter that can run practical, if small, programs.

Readers already familiar with the first edition will find here more detail, and a more interesting language to implement. New readers should already know some programming, especially concerning data structures like lists, dictionaries and stacks. Teaching the basics is outside the scope of this book! Examples will be written in Python, but feel free to use your favorite instead.

Either way, don't forget to enjoy yourself, because that's part of the point.