interpolate.clj

interpolate.clj

;;; ENVIRONMENTAL IMPACT STATEMENT
;;;
;;; This program was written on recycled memory.
;;; No cons cells were created.
;;;

(ns interpolate
  (:use [clojure.walk :only (postwalk)]))

(defmacro s
  "This is my string interpolation macro. There are many like it, but
  this one is ${mine}."
  [tmpl]
  (let [vars (re-seq #"\$\{[^\}]*\}" tmpl)
        strip #(apply str (drop 2 (butlast %)))]
    (list* 'format (reduce #(.replace %1 %2 "%s") tmpl vars)
           (map (comp read-string strip) vars))))

(defmacro interpolating
  "Walks body and interpolates all strings."
  [& body]
  `(do ~@(postwalk #(if (string? %) `(s ~%) %) body)))

(comment
  
  (let [x 10]
    (def y 20)
    (println (s "x is ${x}, y is ${y}, and x+y is ${(+ x y)}")))
  
  (interpolating
   (let [x 20]
     (println "hey there, mr. ${x}! how ya doin?")))
  )