The Scala Either data type

By Alvin Alexander. Last updated: September 16, 2012

URL

http://www.scala-lang.org/api/current/scala/Either.html

The Scala Either data type represents a value of one of two possible types (a disjoint union.) Instances of Either are either an instance of Left or Right.

A common use of Either is as an alternative to Option for dealing with possible missing values. In this usage, scala.None is replaced with a Left which can contain useful information. Right takes the place of Some. Convention dictates that Left is used for failure and Right is used for success.

For example, you could use Either[String, Int] to detect whether a received input is a String or an Int.

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