Tail Call Optimization in Ruby

foo.rb

require './tail_call_optimization'

class Foo
  extend ::TailCallOptimization

  tailrec def fact(n, k = 1)
    raise ArgumentError, 'n should be >= 1' if n < 1
    return k if n == 1
    fact(n - 1, n * k)
  end
end

f = Foo.new
puts f.fact(15_000)

tail_call_optimization.rb

require 'method_source'

module TailCallOptimization
  def tailrec(method_name)
    return if @__performing_tco
    method     = instance_method(method_name)
    file, line = method.source_location
    name, path = File.basename(file), File.path(file)
    options    = {
      tailcall_optimization: true,
      trace_instruction:     false
    }

    RubyVM::InstructionSequence.new(<<-SOURCE, name, path, line - 3, options).eval
      class #{self}
        begin
          @__performing_tco = true
          #{method.source}
        ensure
          remove_instance_variable(:@__performing_tco)
        end
      end
    SOURCE
  end
end