boofoo

anonymous-gist.clj

(defmacro pr-> [& body]
  (let [[init & exprs] body
        syms (repeatedly (count body) gensym)
        vals (mapcat (fn [exp sym prev]
                       [sym `(when-not (instance? Exception ~prev)
                               (try ~(if (seq? exp)
                                       `(~(first exp) ~@(next exp) ~prev)
                                       `(~exp ~prev))
                                    (catch Exception e# e#)))])
               exprs (rest syms) syms)
        ress `(take-while identity ~(vec (rest syms)))]
    `(let ~(vec (concat [(first syms) init] vals))
       (apply print-table
         (format "-> %s" ~init)
         (map vector
           ~(list `quote exprs)
           ~ress))
       (if (instance? Exception (last ~ress))
         (throw (last ~ress))
         (last ~ress)))))

boofoo.core> (pr-> 2 dec dec (/ 1) inc (+ 5))
┌───────┬───────────────────────────────────────────────┐
│ -> 2  │ value                                         │
├───────┼───────────────────────────────────────────────┤
│ dec   ╎ 1                                             │
│ dec   ╎ 0                                             │
│ (/ 1) ╎ java.lang.ArithmeticException: Divide by zero │
└───────┴───────────────────────────────────────────────┘
ArithmeticException Divide by zero  clojure.lang.Numbers.divide (Numbers.java:158)
boofoo.core>