And because in Ruby it is a shortcut, you can invoke it on any object: irb(main):008:0> class Integer irb(main):009:1> def call(b); self.+(b) end i

And because in Ruby it is a shortcut, you can invoke it on any object: irb(main):008:0> class Integer irb(main):009:1> def call(b); self.+(b) end irb(main):010:1> end => :call irb(main):011:0> 1.(2) => 3 :D