Taken from https://github.com/dsl-platform/101-dsl-examples/blob/master/001-periodic-table-of-elements/scala/src/main/scala/com/dslplatform/examples/AsciiTable.scala

Bidirectional maps between values of two key types.

Format a set of ints into a concise textual description.

Example: "2, 5, 7-14, 20"

Implements .equals using reference equality

A partial function that, given a fallback, can efficiently become a total function.

Unfortunately using Nothing results in Scala 2 behaving differently and having lots of problems wrt implicit resolution and type inference.

This is an alternative.

Provides labels based on index for items in an ordered sequence.

Wraps a value such that reference equality holds.

Allows values to be used as map-keys, in sets, etc with uniqueness being by reference.

Conversion to and from roman numerals.

Boolean isomorphism.

Mix into the base type and override companion there.

Examples:

   sealed trait Enabled extends SafeBool[Enabled] {
     override final def companion = Enabled
   }

   case object Enabled extends Enabled with SafeBool.Object[Enabled] {
     override def positive = Enabled
     override def negative = Disabled
   }

   case object Disabled extends Enabled

   sealed abstract class Permission extends SafeBool.WithBoolOps[Permission] {
     override final def companion = Permission
   }

   case object Allow extends Permission
   case object Deny extends Permission

   object Permission extends SafeBool.Object[Permission] {
     override def positive = Allow
     override def negative = Deny
   }

The difference between two sets.

Fast, efficient lookup functions for static data.

Creation verifies key uniqueness and throws runtime exceptions on failure.

Only works with acyclic digraphs. Closure is also reflexive.

Laws

i ∈ [0,size) a2i.i2a = id