with and within

two-useful-macros.clj

(defmacro with
  "do things with the first expression passed,
   and produce the result"
  [expr & body]
  `(let [~'% ~expr] ~@body))

(defmacro within
  "do things with the first expression passed (for side effects),
   but produce the value of the first expression"
  [expr & body]
  `(let [~'% ~expr] ~@body ~'%))

;;----

(facts
 "with and within"
 (with   (+ 1 2 3) (println "x") (println %) (println "y"))
 => nil
 (within (+ 1 2 3) (println "x") (println %) (println "y"))
 => 6

 (with   (+ 1 2 3) (println "x") (println %) (println "y") (inc %))
 => 7
 (within (+ 1 2 3) (println "x") (println %) (println "y") (inc %))
 => 6

 (with-out-str
   (with   (+ 1 2 3) (println "x") (println %) (println "y") (inc %)))
 => "x\n6\ny\n"
 (with-out-str
   (within (+ 1 2 3) (println "x") (println %) (println "y") (inc %)))
 => "x\n6\ny\n"

 (with-out-str
   (-> (+ 1 2)
       (within (println %))
       inc
       (within (println %))
       inc))
 => "3\n4\n"
 (->   (+ 1 2)
       (within (println %))
       inc
       (within (println %))
       inc)
 => 5)