clojure problem halp pls

gistfile1.clj

; given this vector
(def probabilities [ 1 0 0 0.5
                     0 0 1 0 ])

; I want to run (< (rand) probability) against each element

; and ultimately get back either

(def result [ 0 0.75 1.5 ])

; or

(def result [ 0 1.5 ])

; where each row of four, in the above vector, represents row
; index + 0, row + 0.25, row + 0.5, row + 0.75

holy shit, I think I got it

(filter (fn [value] (not (nil? value)))
          (map-indexed (fn [idx prob] (cond (< (rand) prob) (* idx 0.25)))
                                    probabilities))

newb

Beats my effort, I think:

(mapv #(apply + %) (filter #(< (rand) (second %)) (map vector (range 0 (* (count probabilities) 0.25) 0.25) probabilities)))

My result is a vector and not a list, but it's also quite a bit less readable.