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singleton_class? 

        # Module.singleton_class?

(from ruby core)
---
    mod.singleton_class?    -> true or false

---

Returns `true` if *mod* is a singleton class or `false` if it is an
ordinary class or module.

    class C
    end
    C.singleton_class?                  #=> false
    C.singleton_class.singleton_class?  #=> true

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.