rope is still under early development. Check it out if you wish to follow my progress or help, but do not use it in your applications (yet!).

rope is a pure Ruby implementation of the Rope data structure.

For many applications, the Rope class can be a drop-in replacement for String that is optimized for certain use cases.

Using a Rope instance over a String may be desirable in applications that manipulate large amounts of text.

rope currently offers:

Fast string concatenation and substring operations involving large strings
Immutability, which is desirable for functional programming techniques or multithreaded applications

Planned features for rope:

Ability to view a function producing characters as a Rope (including I/O operations). For instance, a piece of a Rope may be a 100MB file, but is only read when that section of the string is examined. Concatenating to the end of that Rope does not involve reading the entire file.
Implement a Rope counterpart to every immutable method available on the String class.

Disadvantages of rope:

Single character replacements are expensive
Iterating character-by-character is slightly more expensive than in a String (TODO: how much? .. haven’t implemented iterators yet)

Installation

rope is hosted on rubygems

gem install rope

… or in your Gemfile

gem 'rope'

rope is tested against MRI 1.8.7 and 1.9.2.

Usage

Creating a Rope

rope = "123456789".to_rope # Rope::Rope.new("123456789") also works

puts rope # "123456789"

Concatenation

A Rope instance can be concatenated with another Rope or String instance.

rope = "12345"
string = "6789"

rope += string
puts rope # "123456789"

Slices/Substrings

A Rope instance offers efficient substring operations. The slice and [] methods are synonymous with their String counterparts.

rope = "123456789".to_rope

puts rope.slice(3, 4) # 4567
puts rope.slice(-6, 4) # 4567
# TODO: More examples when they are implemented

Mutation

A Rope instance reponds to []= similar to String. Mutations to the Rope do not modify the underlying String fragments that constitute the Rope.

rope = "123456".to_rope
rope[1,2] = "foo"
puts rope # 1foo456

loganb / rope