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

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        # Rational.-

(from ruby core)
---
    rat - numeric  ->  numeric

---

Performs subtraction.

    Rational(2, 3)  - Rational(2, 3)   #=> (0/1)
    Rational(900)   - Rational(1)      #=> (899/1)
    Rational(-2, 9) - Rational(-9, 2)  #=> (77/18)
    Rational(9, 8)  - 4                #=> (-23/8)
    Rational(20, 9) - 9.8              #=> -7.577777777777778

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.