if-let++.clj

(defmacro if-let
  "A variation on if-let where all the exprs in the bindings vector must be true and also supports :let."
  ([bindings then]
    `(if-let ~bindings ~then nil))
  ([bindings then else]
    (if (seq bindings)
      (if (= :let (bindings 0))
        `(let ~(bindings 1)
           (if-let ~(subvec bindings 2) ~then ~else))
        `(let [test# ~(bindings 1)]
           (if test#
             (let [~(bindings 0) test#]
               (if-let ~(subvec bindings 2) ~then ~else)))))
      then)))

(defmacro when-let
  "A variation on when-let where all the exprs in the bindings vector must be true and also supports :let."
  [bindings & body]
  `(if-let ~bindings (do ~@body)))