valueopt

Opt - AnyVal Option-like type

Opt is a utility library that provides a fast Option-like type.

The differences of Opt with the standard library Option are:

• Opt is designed to replace Option in hot code paths, or for library methods designed to be used in hot code paths.

• Opt is not fully referentially transparent: the get method throws a NullPointerException

• After the project leaves beta status, the core module, including the structure of the Opt value class itself will not change, guaranteeing binary compatibility.

• Methods such as getOrElse, fold, ... are implemented using macros, and thus produce efficient code that avoids passing closures.

• Opt can store null by using a trick.

• Opt always allocates less memory than Option. It is a value class that erases to a reference type when storing reference types; for primitive types, it stores their boxed versions and erases to a reference type as well. In constrast, Some[Int] allocates an Some instance containing a boxed Int (which could lead or not to an additional allocation).

• Pattern matching on Opt is provided using name-based extractors, to avoid boxing during pattern match (while Option is an algebraic datatype represented by sealed Option and the final Some and None types). Code example:

def testPatternMatch: Unit = {

	val nonEmptyOpt: Opt[Int] = Opt(2)
	val emptyOpt: Opt[Int] = Opt.none[Int] // or OptNone. Opt.none[A] is of type Opt[A]
	
    nonEmptyOpt match {
      case OptSome(x) => println("Success!")
      case OptNone => ??? // is not taken
    }
	
    emptyOpt match {
      case OptSome(x) => ??? // is not taken
      case OptNone => println("Success!")
    }
	
}

Comparable projects

• scala-unboxed-option is our main source of inspiration

• Most complete alternative, including specialized versions for primitive types: arosenberger/nalloc

• xuwei-k/opt

• rklaehn/valueclassoption

Caveats

Code is offered as-is, with no implied warranty of any kind. Comments, criticisms, and/or praise are welcome.

Copyright 2015-2017 Rdiger Klaehn, Erik Osheim, Denis Rosset, Tom Switzer

A full list of contributors can be found in AUTHORS.md.

The MIT software license is attached in the COPYING file.