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@maksbotan
Last active December 16, 2015 00:29
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(define (empty_list selector)
(selector '() '() #t)
)
(define (prepend el lst)
(lambda (selector)
(selector el lst #f)
)
)
(define (head lst)
(lst (lambda (h t e) h))
)
(define (tail lst)
(lst (lambda (h t e) t))
)
(define (is_empty lst)
(lst (lambda (h t e) e))
)
(define (not x)
(if x
#f
#t
)
)
(define (and a b)
(if a
(if b
#t
#f
)
#f
)
)
(define (or a b)
(if a
#t
(if b
#t
#f
)
)
)
(define (map fn l)
(if (is_empty l)
empty_list
(prepend (fn (head l)) (map fn (tail l)))
)
)
(define (filter fn l)
(if (is_empty l)
empty_list
(if (fn (head l))
(prepend (head l) (filter fn (tail l)))
(filter fn (tail l))
)
)
)
(define zero empty_list)
(define (inc n)
(prepend empty_list n)
)
(define (dec n)
(tail n)
)
(define one (inc zero))
(define (add a b)
(if (is_zero b)
a
(add (inc a) (dec b))
)
)
(define (sub a b)
(if (is_zero b)
a
(sub (dec a) (dec b))
)
)
(define (mul a b)
(if (is_zero b)
zero
(add a (mul a (dec b)))
)
)
(define (pow a b)
(if (is_zero b)
one
(mul a (pow a (dec b)))
)
)
(define (is_equal n m)
(if (and (is_zero n) (is_zero m))
#t
(if (or (is_zero n) (is zero m))
#f
(is_equal (dec n) (dec m))
)
)
)
(define (less_than a b)
(if (and (is_zero a) (is_zero b))
#f
(if (is_zero a)
#t
(if (is_zero b)
#f
(less_than (dec a) (dec b))
)
)
)
)
(define (greater_than a b)
(less_than b a)
)
(define (div a b)
(if (less_than a b)
zero
(inc (div (sub a b) b))
)
)
(define (rem a b)
(if (less_than a b)
a
(rem (sub a b) b)
)
)
(define (nth l n)
(if (is_zero n)
(head l)
(nth (tail l) (dec n))
)
)
(define (drop l n)
(if (is_zero n)
l
(drop (tail l) (dec n))
)
)
(define (take l n)
(if (is_zero n)
empty_list
(prepend (head l) (take (tail l) (dec n)))
)
)
(define (slice l start end)
(take (drop l start) (sub end start))
)
(define (length l)
(if (is_empty l)
zero
(inc (length (tail l)))
)
)
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