(defun expression (string &key (supplied-generic-map nil) (conditions-alist *conditions-alist*))
  "Generate an expression object from the provided string."
  (let* ((parsed-string (parsed-string string))
	 (prefix-form (prefix-form parsed-string))
	 (expression-condition (assoc (car prefix-form) conditions-alist))
	 (variable-list (variable-list prefix-form))
	 (generic-map (if (null supplied-generic-map)
			  (generic-map variable-list)
			  supplied-generic-map))
	 (generic-form (generic-form prefix-form generic-map)))
    (make-instance 'expression
		   :string string
		   :prefix-form prefix-form
		   :condition expression-condition
		   :variable-list variable-list
		   :generic-map generic-map
		   :generic-form generic-form)))