;;; CSC 601: More Scheme practice.
;;; Examples from class, Sep 17.

(define atom?
  (lambda (x)
    (not (pair? x))))


(define and~
  (lambda flist
    (lambda (x)      
       (if (null? flist)
          #t
          (and ((car flist) x) ((apply and~ (cdr flist)) x))))))


(define matches?
  ; Match a pattern (tree of predicates) to a tree of objects.
  (lambda (predtree objtree)
    (cond
      ((null? objtree)
       (null? predtree))
      ((atom? objtree)
        ((eval predtree) objtree))
      (#t
       (and (pair? predtree)
            (matches? (car predtree) (car objtree))
            (matches? (cdr predtree) (cdr objtree)))))))

    
(define s
  '(person (name "Tir") (age 25)))

(define s2
  '(person (name "Tir") (age 25) (id 3098098)))

(define s3
  '(person (name "Tir") (age 2.5)))

(define person-
  '(symbol? (symbol? string?) (symbol? (and~ number? positive? integer?))))

  
(matches? person- s ) ;=> #t
(matches? person- s2) ;=> #f
(matches? person- s3) ;=> #f