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Exercise 1.11

(define (recursive-f n)
  (if (< n 3)
    n
    (+ (recursive-f (- n 1))
                    (* 2 (recursive-f (- n 2)))
		    (* 3 (recursive-f (- n 3))))))

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Exercise 1.10

(define (A x y)
	(cond ((= y 0) 0)
				((= x 0) (* 2 y))
				((= y 1) 2)
				(else (A (- x 1)
									(A x (- y 1))))))

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Exercise 1.9

(define (+ a b)
	(if (= a 0)
		b
		(inc (+ (dec a) b))))

;(+ 4 5)
;(inc (+ 3 5))
;(inc (inc (+ 2 5)))

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Exercise 1.2

(/ (+ 5 4 (- 2 (- 3 (+ 6 (/ 4 5)))))
   (* (* 3 (- 6 2)) (- 2 7)))

Exercise 1.3

(define	(sum-of-high-squares a b c)
	(+ (if (> a b) a b) (if (> b c) b c)))

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months_table =
{
  1 => 0,
  2 => 3,
  3 => 3,
  4 => 6,
  5 => 1,
  6 => 4,
  7 => 6,
  8 => 2,

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triangle = [
%w!75!,
%w!95 64!,
%w!17 47 82!,
%w!18 35 87 10!,
%w!20 04 82 47 65!,
%w!19 01 23 75 03 34!,
%w!88 02 77 73 07 63 67!,
%w!99 65 04 28 06 16 70 92!,
%w!41 41 26 56 83 40 80 70 33!,

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def number_under_1000_to_s(n)
  if n == 1000
    'onethousand'
  else
    number_from_999_to_100_to_s(n)
  end
end

def number_from_999_to_100_to_s(n)
  if n > 99

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number = 2**1000

sum = 0

number.to_s.each_char { |n| sum += n.to_i }

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@table = {1 => 1}

result = [0,0]

def next_number(n)
  if n.even?
    n / 2
  else
    3 * n + 1
  end

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class Integer
  
  # overwritten, I don't need modulus
  def sum_progression
    self * (self + 1) / 2
  end
  
  def integral_divisors_size
    factors = self.factors
    result = 1