gistfile1.clj

(defn piece-line-breaks
  "Returns a vector of the indexes of the line breaks in the piece of text"
  [buffer piece]

  (let [text-buffer (if (= (piece :buffer) :source)
                      @(buffer :source)
                      @(buffer :add))]

    (reduce (fn [breaks index]
              (if (= \newline (. text-buffer get index))
                (conj breaks (+ 1 index))
                breaks))
            [] (range 0 (. text-buffer length)))))

Yup, you got it. :-)

Quickie tips, 'cause I can't help myself I guess :-)

• (range (.length text-buffer)) will do
• use (inc index) instead of (+ 1 index) -- the former has a faster inlining