a What to do when a rule matches. Once we have determined which rule to use, we have to determine what it means to use it. The default is just to substitute the bindings of the match into the then-part of the rule.

The rule-based translator tool now looks like this:

(defun rule- based-trans1 ator

(input rules &key (matcher #'pat-match)

(rule-if #'first) (rule-then #'rest) (action #'sub1 is)