logger.clj

;; I use these when I want to throw a lot of `time` functions into code, 
;; as it allows me to append a log to it. Using log-time-str I can 
;; pass the str to whatever logging library I'm using at the time, 
;; to achieve any benefits from that. 

(defmacro log-time
  "prints msg and the approximate number of milliseconds it took to
  eval the given expression. Returns the result of the expr."
  [msg expr]
  `(let [start-time# (System/nanoTime)
         result# ~expr
         elapsed# (- (System/nanoTime) start-time#)]
     (print ~msg "- Elapsed time (ms):" (/ (double elapsed#) 1000000))
     result#))

;; Example
;;   => (log-time "Log This!" (apply + (range 100)))
;;   "Log This! - Elapsed time (ms): 0.092171
;;   4590

(defmacro log-time-str
  "a wrapper around log-time to return the print as a str instead of
  the result of expr. Like clojure.core/pr-str"
  [& args]
  `(with-out-str (log-time ~@args)))