runtime string interpolation

gistfile1.clj

(defmacro capture-values
  "Capture the values of the specified symbols in a symbol->value map."
  [& values]
  (into {} (map (fn [s] [ `'~s s]) values)))

(defn <<!
  "Interpolate a string given a map of symbol->value"
  [f value-map]
  (apply str
         (map (fn [x] (if (symbol? x)
                            (value-map x)
                            (if (seq x)
                              (eval (clojure.walk/prewalk-replace value-map x))
                              x)))
                  (interpolate f))))

(deftest <<!-test
  (testing "runtime docstring examples"
    (let [v 30.5
          m {:a [1 2 3]}]
      (is (= "This trial required 30.5ml of solution."
             (<<! "This trial required ~{v}ml of solution."
                  (capture-values v))))
      (is (= "This trial required 30.5ml of solution."
             (<<! ((fn [] "This trial required ~{v}ml of solution."))
                  (capture-values v))))
      (is (= "There are 30 days in November."
             (<<! ((fn [] "There are ~(int v) days in November."))
                  (capture-values v))))
      (is (= "The total for your order is $6."
             (<<! ((fn [] "The total for your order is $~(->> m :a (apply +))."))
                  (capture-values m)))))
    (is (= "The total for your order is $6."
           (<<! ((fn [] "The total for your order is $~(->> m :a (apply +))."))
                {'m {:a [1 2 3]}})))))