x-hazard-edition.clj

(defn single-return-transducer
  "Dummy transducer that simply returns the value given to it,
  ignoring any accumulated value"
  ([] :initial-value-to-be-ignored)
  ([final-value] final-value)
  ([initial-value v] v))

(defn using-xform--hazard-edition [chunks]
  (transduce (comp (halt-when error?)
                   cat
                   (x/by-key :a x/count)
                   (x/into {}))
             single-return-transducer
             chunks))

(using-xform--hazard-edition chunks)
=> {0 3330, 1 3330, 2 3330}

(using-xform--hazard-edition mini-chunks-with-error)
=> {:error "Something terrible has happened!"}

(criterium/bench (using-xform--hazard-edition chunks))
"
Evaluation count              : 156900 in 60 samples of 2615 calls.
Execution time mean           : 387.491867 µs
Execution time std-deviation  : 17.182729 µs
Execution time lower quantile : 367.187856 µs ( 2.5%)
Execution time upper quantile : 421.113467 µs (97.5%)
Overhead used                 : 1.468563 ns

Found 2 outliers in 60 samples (3.3333 %)
	low-severe	 1 (1.6667 %)
	low-mild	 1 (1.6667 %)
Variance from outliers : 30.3386 % Variance is moderately inflated by outliers
"