Scala has ported the idea of JavaDoc and creatively called it ScalaDoc . Adding ScalaDoc to your Scala source works similarly to adding JavaDoc, and is done with markup in comments (see Figure 5-1). For example, the following fragment in source code

  /** Returns `true` if this value is equal to x, `false` otherwise. **/
  def ==(x: Byte): Boolean

…can be turned into the following fragment in HTML :

Figure 5-1 Embedded ScalaDoc markup gets rendered in HTML

To see the documentation for the Scala Library API, head over to the Scala website.¹ You’ll notice it is broadly similar to JavaDoc. You can see the classes along the left; they’re not grouped by package like in JavaDoc but they’re clickable to get more information.

Figure 5-2 The basic ScalaDoc for Char

A neat feature of ScalaDoc is that you can also filter the content. For example, you can show only methods inherited from Any.

If you’re interested in the hierarchy of a class, you can look at its super-types and subtypes. You may even see a navigable diagram of the type hierarchy, although not every class has this. The type hierarchy diagram for Source in Figure 5-3 shows it is a subtype of Iterable and Closable, and you can navigate up through the hierarchy by clicking on the diagram.

Figure 5-3 ScalaDoc showing the type hierarchy diagram