Dave Thomas ("PragDave")

Dave Thomas, known online as PragDave, co-wrote Programming Ruby, the book most English speakers met Ruby through. Rubyists call it The Pickaxe because of the pickaxe on the cover, and its first edition landed around 2000 (some accounts say 2001). At the time nearly all the Ruby documentation was in Japanese, so a friendly, thorough English guide is a large part of why the language spread beyond Japan at all. He found Ruby in 1998, fell for it, and, by his own account, spent the next decade evangelizing it. Later editions were written with Chad Fowler and Andy Hunt. (One quick note for newcomers: this is not the Dave Thomas who founded Wendy’s, nor any of the other programmers who share the name.)

Ruby is far from his only mark on the craft. With Andy Hunt he co-wrote The Pragmatic Programmer (1999), one of the best-selling books in the field, and the two of them founded The Pragmatic Bookshelf, the publisher behind hundreds of developer titles. He was one of the seventeen authors of the 2001 Manifesto for Agile Software Development, and he is credited with popularizing the principle DRY (“Don’t Repeat Yourself”) and the practice of the Code Kata, small exercises for deliberately practicing programming.

He is also often credited, within the Ruby community, with popularizing Duck Typing: the idea that what matters about an object is what it can do, not what class it belongs to. Here the history is genuinely murky, so treat any tidy origin story with care. Wikipedia’s own article on duck typing names no single coiner, and an early programmer use of the exact phrase is instead attributed to Python’s Alex Martelli in a July 2000 mailing-list post. What is safe to say is that the concept became central to how Rubyists think and write, and the Pickaxe helped spread that vocabulary.

Related: The Pickaxe · Duck Typing · Chad Fowler · Yukihiro "Matz" Matsumoto