(defmacro for (var start stop &body body);creates a for loop that mimics c's for, kinda
  (let ((gstop (gensym)));create a lexically unique variable
    `(do ((,var ,start (1+ ,var));this is the list that injected into source. (do ((x 1 (1+ x))
          (,gstop ,stop));gstop = stop
        ((> ,var ,gstop));stop when var > gstop
      ,@body)));else, do body
      
(defmacro in (obj &rest choices);is the first parameter in the remaining parameters
  (let ((insym (gensym)));lexically unique var.
    `(let ((,insym ,obj));set the var to what we are searching for
      (or ,@(mapcar #'(lambda (c) `(eql ,insym ,c));and check to see if obj is in choices by using mapcar
                    choices)))))
                    
(defmacro random-choice (&rest exprs);choises one from the list of parameters
  `(case (random ,(length exprs))
    ,@(let ((key -1))
        (mapcar #'(lambda (expr)
                    `(,(incf key) ,expr))
                exprs))))
                
(defmacro avg (&rest args);gets the average of the parameters
  `(/ (+ ,@args) ,(length args)))
  
(defmacro with-gensyms (syms &body body);useful to use in a macro, defines many gensyms.
  `(let ,(mapcar #'(lambda (s)
                     `(,s (gensyms)))
                 syms)
    ,@body))
    
(defmacro aif (test then &optional else)
  `(let ((it ,test))
    (if it ,then ,else)))
    
(deftest test-utility-macros ()
  (let ((total 0))
    (check
      (in 5 1 2 3 4 5 6)
      (not (in 6 1 2 3 4 5))
      (random-choice 'a 'b 'c 'd)
      (= (avg 1 2 3 4 5) 3)
      (aif (> (+ 1 2) 2) t nil)
)))