This is a Ruby tree! It shows every object from the Ruby Programming Language in a tree format.

<=> 

        # Module.<=>

(from ruby core)
---
    module <=> other_module   -> -1, 0, +1, or nil

---

Comparison---Returns -1, 0, +1 or nil depending on whether `module`
includes `other_module`, they are the same, or if `module` is included
by `other_module`.

Returns `nil` if `module` has no relationship with `other_module`, if
`other_module` is not a module, or if the two values are incomparable.

This is MURDOC! A Ruby documentation browser inspired by Smalltalk-80. It allows you to learn about Ruby by browsing through its class hierarchies, and see any of its methods.