D. Richard Hipp used TACOP to implement a B-tree for SQLite:

> "Nobody ever taught me about a B-tree. I had heard of it. When I went to write my own B-tree, on the bookshelf behind me, I’ve got Don Knuth’s The Art of Computer Programming, so I just pulled that down, I flipped to the chapter on searching and looked up B-trees and he described the algorithm. That’s what I did. Funny thing, Don gives us details on the algorithm for searching a B-tree and for inserting into a B-tree. He does not provide an algorithm for deleting from the B-tree. That’s an exercise at the end of the chapter, so before I wrote my own B-tree I had to solve the exercise at the end. Thanks, Don. I really appreciate it."

https://corecursive.com/066-sqlite-with-richard-hipp/#b-tree...