number.egi

;;;;;
;;;;;
;;;;; Number
;;;;;
;;;;;

;;;
;;; Natural Numbers
;;;
(define $nat
  (matcher
    {[,$n []
      {[$tgt (if (eq? tgt n) {[]} {})]}]
     [<o> []
      {[0 {[]}]
       [_ {}]}]
     [<s $> nat
      {[$tgt (match (compare tgt 0) ordering
               {[<greater> {(- tgt 1)}]
                [_ {}]})]}]
     [$ [something]
      {[$tgt {tgt}]}]
     }))

(define $nats {1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 @(map (+ 100 $) nats)})

(define $nats0 {0 @nats})

(define $odds {1 @(map (+ $ 2) odds)})

(define $evens {2 @(map (+ $ 2) evens)})

(define $fibs {1 1 @(map2 + fibs (cdr fibs))})

(define $prime?
  (lambda [$n]
    (not (any 1#(eq? (remainder n %1) 0)
              (while (lte? $ (floor (sqrt (itof n)))) primes)))))

(define $primes {2 @(filter prime? (drop 2 nats))})

(define $divisor?
  (lambda [$n $d]
    (eq? 0 (remainder n d))))

(define $find-factor
  (lambda [$n]
    (match primes (list integer)
      {[<join _ <cons (& ?(divisor? n $) $x) _>> x]})))

(define $prime-factorization
  (match-lambda integer
    {[,1 {}]
     [$n (let {[$p (find-factor n)]}
           {p @(prime-factorization (quotient n p))})]}))

(define $p-f prime-factorization)

(define $even?
  (lambda [$n]
    (eq? 0 (modulo n 2))))

(define $odd?
  (lambda [$n]
    (eq? 1 (modulo n 2))))

(define $square?
  (lambda [$n]
    (let {[$x (round (sqrt n))]}
      (eq? n (power x 2)))))

(define $gcd
  (lambda [$ns]
    (match ns (multiset integer)
      {[<cons $n <nil>> n]
       [<cons (& ,(min ns) $m) $rs>
        (gcd {m @(delete 0 (map (lambda [$r] (modulo r m)) rs))})]})))

(define $fact
  (lambda [$n]
    (foldl * 1 (between 1 n))))

(define $perm
  (lambda [$n $r]
    (foldl * 1 (between (- n (- r 1)) n))))

(define $comb
  (lambda [$n $r]
    (/ (perm n r)
       (fact r))))

;;;
;;; Integers
;;;
(define $mod
  (lambda [$m]
    (matcher
      {[,$n []
        {[$tgt (if (eq? (modulo tgt m) (modulo n m))
                   {[]}
                   {})]}]
       [$ [something]
        {[$tgt {tgt}]}]
       })))

(define $power
  (lambda [$x $n]
    (foldl * 1 (take n (repeat1 x)))))

(define $sum
  (lambda [$xs]
    (foldl + 0 xs)))

(define $product
  (lambda [$xs]
    (foldl * 1 xs)))

;;;
;;; Decimal Fractions
;;;
(define $rtod-helper
  (lambda [$m $n]
    (let {[$q (quotient (* m 10) n)]
          [$r (remainder (* m 10) n)]}
      {[q r] @(rtod-helper r n)})))

(define $rtod
  (lambda [$c $x]
    (let* {[$m (numerator x)]
           [$n (denominator x)]
           [$q (quotient m n)]
           [$r (remainder m n)]}
      [q (take c (map fst (rtod-helper r n)))])))

(define $rtod'
  (lambda [$x]
    (let* {[$m (numerator x)]
           [$n (denominator x)]
           [$q (quotient m n)]
           [$r (remainder m n)]
           [[$s $c] (find-cycle (rtod-helper r n))]}
      [q (map fst s) (map fst c)])))

(define $show-decimal
  (lambda [$c $x]
    (match (rtod c x) [integer (list integer)]
      {[[$q $sc] (foldl S.append (S.append (show q) ".") (map show sc))]})))

(define $show-decimal'
  (lambda [$x]
    (match (rtod' x) [integer (list integer) (list integer)]
      {[[$q $s $c] (foldl S.append "" {(S.append (show q) ".") @(map show s) " " @(map show c) " ..."})]})))

;;;
;;; Continued Fraction
;;;
(define $regular-continued-fraction
  (lambda [$as]
    (+ (car as)
       (foldr (lambda [$a $r] (/ 1 (+ a r)))
              0
              (cdr as)))))


(define $continued-fraction
  (match-lambda [(list integer) (list integer)]
    {[[<cons $a $as> <cons $b $bs>]
      (+ a (/ b (continued-fraction as bs)))]
     [[<cons $a <nil>> <nil>] a]}))

(define $regular-continued-fraction-of-sqrt
  (lambda [$n]
    undefined))