Something like:

(defn safe-sum [coll]
  (reduce (fn [s x] (if x (+ x s) (reduced s))) coll))

This will compute the sum until it hits a "falsey" (i.e. nil or false)
value. Alternatively, you could write it:

(defn safe-sum [coll]
  (apply + (take-while identity coll)))

- James


On 24 November 2013 17:13, David Simmons <shortlypor...@gmail.com> wrote:

> Hi Stu
>
> I understand Reduce but can't quite see how this would work. Don't suppose
> you'd have a simple example would you?
>
> Many thanks
>
> Dave
>
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