1.9 KiB
Brolib-sml
Introduction
Standard ML port of this rope implementation.
This particular rope uses the balancing scheme described in the Purely Functional 1-2 Brother Trees paper authored by Ralph Hinze. It tries to keep the number of nodes to a minimum by joining the strings in adjacent leaf nodes, if joining would not be too expensive.
Usage
The two files are rope.sml and tiny_rope.sml.
rope.sml contains a rope that tracks line metadata (which has a small performance and memory penalty). This is useful if you have line-based operations in mind.
tiny_rope.sml doesn't track line metadata, and is useful when line-queries aren't needed.
Except for the line-based operations appendLine and foldLines, all functions are the same between the two (aside from verifyLines which is just for testing purposes).
Examples of usage can be found in examples.sml.
Performance
These two ropes are both quite fast. I compared the OCaml port with the other text data structures in OCaml, and it beat those handily when processing the datasets from here which just test insertion and deletion. It was also faster at performing substrings than the others.
I don't know other Standard ML libraries to compare it to, but with MLton, this rope implementation beats the fastest ropes in Rust at insertion and deletion quite easily, never going 1 ms in the slowest dataset.
I don't know how to explain this result, but I assume most of the credit goes to the MLton compiler. It also seems likely that this is slower or string queries, as those Rust implementations use cache-friendly B-Trees as opposed to the binary tree used here.
(Note to self: worth giving numbers.)