condx: extends cond to allow 'if-let' style binding forms.

gistfile1.clj

(defmacro condx-aux [f & clauses]
  (when clauses
    (list f (first clauses)
          (if (next clauses) (second clauses)
              (throw (IllegalArgumentException. "condx requires an even number of forms")))
          (cons 'condx (next (next clauses))))))

(defmacro condx
  "condx extends cond to allow 'if-let' style binding forms.
   Example:
   (condx [x (re-matches #\"\\((.+)\\)\\s*\\[(.+)\\]\\s*(.+)\" s)] {:category (nth x 1) :author (nth x 2) :title (nth x 3)}
          [x (re-matches #\"\\[(.+)\\]\\s*(.+)\" s)] {:author (nth x 1) :title (nth x 2)}
          (= 0 (.length s)) "NO TITLE"
          :else {:title s})"
  [& clauses]
  (when clauses
    (if (vector? (first clauses))
      `(condx-aux if-let ~@clauses)
      `(condx-aux if ~@clauses))))