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

Math::DomainError

        # Math::DomainError < StandardError

(from ruby core)
---
Raised when a mathematical function is evaluated outside of its domain
of definition.

For example, since `cos` returns values in the range -1..1, its inverse
function `acos` is only defined on that interval:

    Math.acos(42)

*produces:*

    Math::DomainError: Numerical argument is out of domain - "acos"
---

      

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.