RingSeq

A library that adds new operations to Scala Seq for when a sequence needs to be considered circular, its elements forming a ring.

It works on any immutable / mutable Seq and sub-types.

Available for Scala 3.3.1 and 2.13.13, compatible with Scala.js

Setup

Add the following dependency to your build.sbt file:

libraryDependencies += "io.github.scala-tessella" %% "ring-seq" % "0.6.2" // Use %%% instead of %% if you're using ScalaJS

Getting started

First, start with the following import:

import io.github.scala_tessella.ring_seq.RingSeq._

Where the RingSeq object is imported, any collection under Seq will access the new methods. You can write something like:

"RING".rotateRight(1).mkString // GRIN
List(0, 1, 2, 3).startAt(2) // List(2, 3, 0, 1)
ListBuffer(1, 3, 5, 7, 9).reflectAt(3) // ListBuffer(7, 5, 3, 1, 9)

Need

Whenever data are structured in a circular sequence, chances are you don’t want to locally reinvent the wheel (pun intended).

Solution

RingSeq is a small, purely functional, self-contained library, where most of the circular use cases are already solved and building blocks provided for the others.

Leveraging Scala 3 extension or Scala 2 implicit class, it acts like a decorator, providing new circular methods to any collection under Seq.

Design

The same decorators could possibly be added to scala-collection-contrib and exist just there, but the underlying design has (at least for me) a very steep learning curve and the community help is weak. One clear maintenance advantage would be that the source code is the same for Scala 2.13 and Scala 3.

So, for now, is a conscious decision to achieve the same results with a simpler design (even if the source code is different between Scala 2.13 and Scala 3) and to publish in this, concise and hopefully useful, separate library.

Other languages

The same library is available also for the Python language, check RingSeqPy (Python version).