anchor.diff:  (defun _i (i v)
     (declare (ignore v))
     i)
  +
  
positive.code:                                  (if (consp c)
                                       (create-col (car c)
                                                   (get-pos :db ',db :table tbl)
                                                   :pred (eval (cdr c)))
                                       (create-col c
                                                   (get-pos :db ',db :table tbl))))
                               cols))
  
negative.code: 
  (defun first-nil (arr)
    (loop :for i :from 0 :to (1- (length arr))
          :when (null (aref arr i))
            :return i
          :finally (return -1)))
  
  (defun lookup-table (name table)
    (loop :for i :from 0 :to (1- (length table))
          :when (equal name (getf (aref table i) :name))
            :return (getf (aref table i) :data)
          :finally (return 'DNE)))
  
  (defstruct db
    (name nil :type symbol)
  