# Purely Functional Data Structures by Chris Okasaki

8 Hacker News commenters recommended Purely Functional Data Structures by Chris Okasaki and 1 criticized it, November 2025 to November 2026. It was recommended in 5 of 13 months.

**Verdict:** Readers call it a classic reference on functional data structures, praising its clear insights and fast, readable presentation.

## Why people recommend it

- Clear, insightful, fast-moving presentation (2 comments): "there's a feel to Hairer's and Okasaki's insights and presentation that simply is not going to be reached" ([source](https://news.ycombinator.com/item?id=49123299)) "Very soothing and moves fast." ([source](https://news.ycombinator.com/item?id=49120803))
- Highly regarded by readers (2 comments): "Okasaki's is basically the Bible for this stuff." ([source](https://news.ycombinator.com/item?id=46156688)) "great book and great dude" ([source](https://news.ycombinator.com/item?id=48692579))

## Alternatives hackers recommend

- [Crafting Interpreters by Robert Nystrom](https://hackerapproved.com/p/crafting-interpreters.md): 60 recommend
- [Clean Code by Robert C. Martin](https://hackerapproved.com/p/clean-code.md): 31 recommend
- [The Pragmatic Programmer by Hunt and Thomas](https://hackerapproved.com/p/pragmatic-programmer.md): 28 recommend
- [How to Design Programs by Felleisen, Findler, Flatt and Krishnamurthi](https://hackerapproved.com/p/how-to-design-programs.md): 18 recommend
- [Mastering Emacs by Mickey Petersen](https://hackerapproved.com/p/mastering-emacs.md): 17 recommend

## Where to get it

- [See price on Amazon](https://www.amazon.com/dp/0511825137?tag=hackerapprove-20) (affiliate link)
- [Bookshop.org](https://bookshop.org/a/130825/9780511825132) (affiliate link)

## Cite as

Hacker Approved, "Purely Functional Data Structures by Chris Okasaki", https://hackerapproved.com/p/purely-functional-data-structures/ (counts from 1,795,640 Hacker News comments, November 2025 to November 2026).