Shares many aspects with functional languages such as Lisp and Scheme

• Numerous iterators (.each, .map, .select, .find, .sort_by, .delete_if)
• Closures / blocks – function literals that are first-class objects enabling higher-order functions
• Method chaining
• 'if' is an expression, not a statement, and thus returns a value
  • So are 'unless', 'until', and 'while'
• Programs may thus be modeled according to OO, functional, or procedural principles – flexibility