Matching and Substitution

Matching and substitution can be combined to transform an input based on a rewrite rule: a list of an input pattern and an output pattern:

( (- (+ ?x ?y) (+ ?z ?y))   (- ?x ?z) )

(defun transf (rule input)   ; simple version
  (let (bindings)
    (if (setq bindings
              (match (first rule) input))
        (sublis bindings (second rule))) ))

(match '(- (+ ?x ?y) (+ ?z ?y))
       '(- (+ (age tom) (age mary))
           (+ (age bill) (age mary))))

((?Z AGE BILL) (?Y AGE MARY) (?X AGE TOM) (T . T))

(transf '((- (+ ?x ?y) (+ ?z ?y))
          (- ?x ?z))
        '(- (+ (age tom) (age mary))
            (+ (age bill) (age mary))))


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