Look and say, ruby & clojure

look_and_say.clj

(ns look-and-say)

(defn- consecutive [string]
  (map first (re-seq #"(.)\1*" string)))

(defn- say [chars]
  [(count chars) (first chars)])

(defn- get-next [string]
  (apply str (mapcat say (consecutive string))))

(defn look-and-say [string]
  (iterate get-next string))

; (def las (look-and-say/look-and-say "1"))
; (take 2 las)
; => ("1" "11")
; (take 2 las)
; => ("1" "11")

look_and_say.rb

module LookAndSay
  class << self
    def look_and_say(string)
      Enumerator.new do |yielder|
        current = string
        loop do
          yielder << current
          current = get_next current
        end
      end
    end

    private

    def consecutive(string)
      string.scan(/((.)\2*)/).map &:first
    end

    def say(chars)
      [chars.length, chars[0]]
    end

    def get_next(string)
      consecutive(string).map(&method(:say)).join ''
    end
  end
end

# las = LookAndSay.look_and_say '1'
# las.take 2
# => ["1", "11"]
# las.take 2
# => ["1", "11"]

Ah... heh. Well, for my solution, yeah, #take doesn't work perfectly. There's a slightly longer way to write it where it works correctly, but harder to fit into a tweet:

def iterate(meth, arg)
  Enumerator.new do |yielder|
    current = arg
    loop do
      yielder << current
      current = send(meth, current)
    end
  end
end

By reassigning the method parameter, it prevents #take from working correctly.