Some `if`/`when` helpers. Don't need these often (and avoid them whenever possible), but they're occasionally handy when dealing with particularly hairy code.

more-ifs.clj

(defmacro iff [test & {:keys [then else]}] `(if ~test ~then ~else))
(comment (iff false
              :then (println "true")
              :else (println "false")))

(defmacro iff-let [bindings & {:keys [then else]}] `(if-let ~bindings ~then ~else))
(comment (iff-let [x true] :else "false" :then x))

(defmacro if-lets
  "Like `if-let` but binds multiple values iff all tests are true."
  ([bindings then] `(if-lets ~bindings ~then nil))
  ([bindings then else]
     (let [[b1 b2 & bnext] bindings]
       (if bnext
         `(if-let [~b1 ~b2] (if-lets ~(vec bnext) ~then ~else) ~else)
         `(if-let [~b1 ~b2] ~then ~else)))))

(comment (if-lets [a :a]  a)
         (if-lets [a nil] a)
         (if-lets [a :a b :b]  [a b])
         (if-lets [a :a b nil] [a b]))

(defmacro iff-lets [bindings & {:keys [then else]}] `(if-lets ~bindings ~then ~else))

(defmacro when-lets
  "Like `when-let` but binds multiple values iff all tests are true."
  [bindings & body]
  (let [[b1 b2 & bnext] bindings]
    (if bnext
      `(when-let [~b1 ~b2] (when-lets ~(vec bnext) ~@body))
      `(when-let [~b1 ~b2] ~@body))))

(comment (when-lets [a :a b nil] "foo"))