# Is there a better way to extract a single value instead of a sequence?

The following code works, but I'd like to re-write, so that a single index is returned, rather than a sequence of indexes visited.

Here are the defs and function.

(def usage-vec-len 13)
(def read-levels [9999 3000 2000 1000 100 90 80 70 60 50 40 30 10])
"Finds the correct position at which to bin part of the reading."
(for [idx (reverse (range 0 usage-vec-len))
:let [out-idx idx]
out-idx))


If I run this with a reading of 5, I get what I expect

wtr-usage1.core=> (sel-adj-idx 5)
(12 11 10 9 8 7 6 5 4 3 2 1 0)
0
wtr-usage1.core=>


I keep going until the first index. The value of 5 would be binned there. I would like just to return the index, but still need to traverse read-levels to compare the reading against each of the levels.

Is there a better form to use for this purpose? I could probably write this recursively, but am trying to see if I can do it with Clojure's rich set of sequence functions.

• Why not use just what you posted? Like this:

;use better names

• for is used to generate sequences. Try loop for more general looping needs.

• You should not hard code the length of a data structure. Each time you update read-levels you will need to update usage-vec-len. Use count instead. It is supposed to be fast for vectors.

• A suggestion follows, Not a clojure programmer, so ignore the style:

(defn bin-idx [reading]
"......"
(second (first (drop-while #(> reading (first %))
(map vector
(range))))))


(def ^:const read-levels [10 30 40 50 60 70 80 90 100 1000 2000 3000 9999]

(defn bin-index [level]
"Finds the correct position at which to bin part of the reading."