Purely Functional Data Structures
Purely Functional Data Structures by Chris Okasakiby Chris Okasaki
Shares rank 18 of 115 programming books by recommenders
Readers call it a classic reference on functional data structures, praising its clear insights and fast, readable presentation.
Readers call it a classic reference on functional data structures, praising its clear insights and fast, readable presentation.
9 people gave an opinion
- recommend it
- 8
- criticize it
- 1
- approval share
- 89%
Recommended in 5 of 13 months
- November 2025: not recommended
- December 2025: recommended
- January 2026: not recommended
- February 2026: not recommended
- March 2026: not recommended
- April 2026: recommended
- May 2026: recommended
- June 2026: recommended
- July 2026: recommended
- August 2026: not recommended
- September 2026: not recommended
- October 2026: not recommended
- November 2026: not recommended (month in progress)
Why it doesn’t carry the badge
- 8 people recommend itNeeds 10 or more, not met.
- 8 recommenders for every criticNeeds 2 to 1 or better, met.
- Recommended in 5 of 13 monthsNeeds 4 or more, met.
The same three rules apply to every product, and the badge can’t be bought. How the badge works
What people say about it
The reasons people give, with the number of comments that give each one. Open a reason to read what they said.
Why people recommend it
Each mark is one comment
Clear, insightful, fast-moving presentation
“there's a feel to Hairer's and Okasaki's insights and presentation that simply is not going to be reached”
Comment from 31 Jul 2026 in “"the very foundation of modern academia has been blown to bits"” “Very soothing and moves fast.”
Comment from 31 Jul 2026 in “"the very foundation of modern academia has been blown to bits"” Highly regarded by readers
“Okasaki's is basically the Bible for this stuff.”
Comment from 5 Dec 2025 in “Functional Quadtrees” “great book and great dude”
Comment from 26 Jun 2026 in “Bipartite Matching Is in NC”
Other programming books people recommend
The four most recommended other programming books, with the same counts for each, so you can compare like for like. The tick on each bar marks the 2 to 1 line the badge needs.
| Product | Recommend | Criticize | Approval | Months | Owned | Badge |
|---|---|---|---|---|---|---|
| Crafting Interpretersby Robert Nystrom | 60 | 4 | 94% | 10 | — | Approved |
| Clean Codeby Robert C. Martin | 31 | 87 | 26% | 9 | — | — |
| The Pragmatic Programmerby Andy Hunt and Dave Thomas | 28 | 1 | 97% | 7 | — | Approved |
| How to Design Programsby Matthias Felleisen and Robert Bruce Findler and Matthew Flatt and Shriram Krishnamurthi | 18 | 2 | 90% | 7 | — | Approved |
| Purely Functional Data Structuresby Chris OkasakiThis page | 8 | 1 | 89% | 5 | — | — |
What people said
6 of the 9 comments that mention it, newest first. Each links to the original comment.
“there's a feel to Hairer's and Okasaki's insights and presentation that simply is not going to be reached”
“Very soothing and moves fast.”
“great book and great dude”
“It was still fairly relevant”
“it also doesn't contain that many data structures”
“Okasaki's is basically the Bible for this stuff.”
Counts come from 1,795,640 Hacker News comments, November 2025 to November 2026. How we count. Report a mistake.