check-macro.clj

(defmacro check
  "Takes an expression and optional test functions,
  returning the value of the expr if it is non-nil and passes the tests,
  throwing an exception otherwise.
  Examples:
  (check (+ 1 2) (partial = 3)) => 3
  (check (+ 1 2) (partial odd?) (partial even?) => throws Exception
  (check (.toUpperCase \"okay\")) => \"OKAY\"
  (check nil) => throws Exception"
  ([expr & tests]
   (let [tests# (map (fn [t] [t (str t)]) tests)] ;; need both the test and its form
     `(let [value# ~expr]
        (doseq [[test# test-form#] [~@tests#]]
          (when (not (test# value#))
            (throw (Exception. 
                     (str (quote ~expr) 
                       " failed check: " test-form# 
                       " with value: " value#)))))
        value#)))
  ([expr]
   (let [value# expr]
     `(if ~value# ~value#
        (throw (Exception. (str (quote ~expr) " was nil")))))))