Exemplo de programação funcional em Ruby

funcs.rb

multiple = -> num_one { 
  return -> num_two {
    num_one * num_two
  }
}
# => Proc

double = multiple.call 2
# => Proc
triple = multiple.call 3
# => Proc

ten_double  = double.call 10
# => 20
six_double  = double.call 6
# => 12
five_triple = triple.call 5
# => 15