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

IndexError 

        # IndexError < StandardError

(from ruby core)
---
Raised when the given index is invalid.

    a = [:foo, :bar]
    a.fetch(0)   #=> :foo
    a[4]         #=> nil
    a.fetch(4)   #=> IndexError: index 4 outside of array bounds: -2...2
---

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.