Implementing Infinite Data Structure in JavaScript.

== 11/26 ==
 * naturalSequence().filter(limit(n)).reduce(sum)
  * sum(a, b) := a + b
  * limit(n)(a) := (n >= a)
  * .reduce(f(a, b)) := f(seq[:last-1].reduce(f), seq[last])
  * filter(f(a)) := for each a in seq, sequence of a which f(a) is true.