On Oct 19, 4:54 am, Alex Osborne <a...@meshy.org> wrote:
> (reduce-by record-type
> (fn [count data] (+ count (units data)))
> 0 (get-idata))
Wow - that is a really nice abstraction!
Kind of leads to SQLalike queries:
(defn select-count
[grouper coll]
(reduce-by grouper (fn [x _] (inc x)) 0 coll))
(defn select-sum
[summer grouper coll]
(reduce-by grouper (fn [x row] (+ x (summer row))) 0 coll))
(let [owners #{{:name "dorris" :sale 5}
{:name "joe" :sale 2}
{:name "dorris" :sale 2}
{:name "joe" :sale 2}
{:name "carol" :sale 2}
{:name "louise" :sale 2}}]
(select-sum :sale :name owners))
#_({"carol" 2, "dorris" 7, "joe" 2, "louise" 2})
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