;; test functions and definitions for MiniScheme project


(define nil ())

(define reverse 
  (lambda (x)
    (define reverseh 
      (lambda (y a)
	(cond ((null? y) a)
	      (#t (reverseh (cdr y) (cons (car y) a))))))
    (reverseh x nil)))


(define and 
  (lambda (x y)
    (cond (x y)
	  (#t #f))))

(define equal?
  (lambda (x y)
    (cond ((and (atom? x) (atom? y)) (eq? x y))
	  ((atom? x) nil)
	  ((atom? y) nil)
	  (#t (and (equal? (car x) (car y)) (equal? (cdr x) (cdr y)))))))

(define map
  (lambda (f l)
    (cond ((null? l) nil)
	  (#t (cons (f (car l)) (map f (cdr l)))))))

(define filter
  (lambda (pred l)
    (cond ((null? l) nil)
	  ((pred (car l)) (filter pred (cdr l)))
	  (#t (cons (car l) (filter pred (cdr l)))))))

(define insert
  (lambda (e l)
    (cond ((null? l) (cons e l))
	  ((< e (car l)) (cons e l))
	  (#t (cons (car l) (insert e (cdr l)))))))

(define isort
  (lambda (l)
    (define isort-help
      (lambda (l sorted-l)
	(cond ((null? l) sorted-l)
	      (#t (isort-help (cdr l) (insert (car l) sorted-l))))))
    (isort-help l nil)))

(define append 
  (lambda (x y)
    (cond ((null? x) y)
	  (#t (cons (car x) (append (cdr x) y))))))