Equal

statement

Equal is a small library for Scala to provide zero-overhead type-safe equals and not-equals operators === and !==.

It is (C)opyright 2016–2020 by Hanns Holger Rutz. All rights reserved. Equal is released under the GNU Lesser General Public License v2.1+ and comes with absolutely no warranties. To contact the author, send an e-mail to contact at sciss.de.

Warning: This is not yet thoroughly tested.

N.B.: Currently only Scala 2 on JVM performs extra type-safety checks, whereas Scala.js and Dotty use a simple equality check without added type-safety. So make sure you always cross-compile your project with Scala 2.12 or 2.13 on the JVM.

requirements / installation

This project builds with sbt against Scala 2.13, 2.12, Dotty (JVM) and Scala 2.13 (JS). The last version to support Scala 2.11 was v0.1.4.

To use the library in your project:

"de.sciss" %% "equal" % v

The current version v is "0.1.6"

contributing

Please see the file CONTRIBUTING.md

documentation

You import the operators using

import de.sciss.equal.Implicits._

Then the following compiles:

Vector(1, 2, 3) === List(1, 2, 3)   
"hello" !== "world"
4 !== 5
Option("foo") !== None
List(Some(1), None) === Seq(Some(1), None)

def contains[A](in: Option[A], elem: A): Boolean = in === Some(elem)

While the following does not:

Vector(1, 2, 3) === Set(1, 2, 3)    // to-do: mysterious error message
List(1, 2) === ((1, 2))
4 !== 5f
"hello" === Some("hello")

def contains[A, B](in: Option[A], elem: B): Boolean = in === Some(elem)