I want to do the following in Clojure as idiomatically as possible:
Is there a succinct way to do this using core library functions?
If not, what improvements can you suggest to the following implementation?
(defn to-hash [coll xform]
(reduce
merge
(map
#(apply hash-map %)
(mapcat hash-map coll (into [] xform coll)))))
something like this should do the trick without intermediate collections:
(defn process [data xform]
(zipmap data (eduction xform data)))
user> (process [1 2 3] (comp (map inc) (map #(* % %))))
;;=> {1 4, 2 9, 3 16}
the docs on eduction say the following:
Returns a reducible/iterable application of the transducers to the items in coll. Transducers are applied in order as if combined with comp. Note that these applications will be performed every time reduce/iterator is called.
so no additional collection is created.
This is any good, of course, as long as there is one-to-one relationship between input and output elements. What is desired output for (process [1 -2 3] (filter pos?))
or (process [1 1 1 2 2 2] (dedupe))
?
(by the way, your to-hash
implementation has the same flaw)
Indeed, the problem I am solving uses non-filtering transducers. I should have mentioned that in the opening post! Your implementation is exactly what I was looking for.