About

True, False

• true and false are used to represent boolean logical states.
  • They are singleton instances of the TrueClass and FalseClass objects.
  • they may occur as literals in code, or as the result of logical (&&, ||, !) or comparison (<, >, ==) methods.

Truthy and falsey

• When not using strict Boolean values, truthy and falsey evaluation rules are applied:

  • Only false and nil evaluates as falsey.
  • Everything else evaluates as truthy.

  # A simplified definition
  def falsey
    nil || false
  end
  
  def truthy
    not falsey
  end

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Originally from Exercism ruby concepts