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  1. ; three simple math problems
  2.  
  3. (define-syntax fold-of
  4.   (syntax-rules (range in is)
  5.     ((_ "z" f b e) (set! b (f b e)))
  6.     ((_ "z" f b e (v range fst pst stp) c ...)
  7.       (let* ((x fst) (p pst) (s stp)
  8.              (le? (if (positive? s) =)))
  9.         (do ((v x (+ v s))) ((le? p v) b)
  10.           (fold-of "z" f b e c ...))))
  11.     ((_ "z" f b e (v range fst pst) c ...)
  12.       (let* ((x fst) (p pst) (s (if (< x p) 1 -1)))
  13.         (fold-of "z" f b e (v range x p s) c ...)))
  14.     ((_ "z" f b e (v range pst) c ...)
  15.       (fold-of "z" f b e (v range 0 pst) c ...))
  16.     ((_ "z" f b e (x in xs) c ...)
  17.       (do ((t xs (cdr t))) ((null? t) b)
  18.         (let ((x (car t)))
  19.           (fold-of "z" f b e c ...))))
  20.     ((_ "z" f b e (x is y) c ...)
  21.       (let ((x y)) (fold-of "z" f b e c ...)))
  22.     ((_ "z" f b e p? c ...)
  23.       (if p? (fold-of "z" f b e c ...)))
  24.     ((_ f i e c ...)
  25.       (let ((b i)) (fold-of "z" f b e c ...)))))
  26.  
  27. (define-syntax list-of (syntax-rules ()
  28.   ((_ arg ...) (reverse (fold-of
  29.     (lambda (d a) (cons a d)) '() arg ...)))))
  30.  
  31. (define (isqrt n)
  32.   (if (not (and (positive? n) (integer? n)))
  33.       (error 'isqrt "must be positive integer")
  34.       (let loop ((x n))
  35.         (let ((y (quotient (+ x (quotient n x)) 2)))
  36.           (if (< y x) (loop y) x)))))
  37.  
  38. (define (square? n) (let ((s (isqrt n))) (= (* s s) n)))
  39.  
  40. (define (fact n) (if (zero? n) 1 (* n (fact (- n 1)))))
  41.  
  42. (display
  43.   (do ((y 10 (+ y 1)))
  44.       ((square? (- (expt 2 y) 615))
  45.         (list (isqrt (- (expt 2 y) 615)) y))))
  46. (newline)
  47.  
  48. (display
  49.   (list-of (list a b c)
  50.     (a range 1 10)
  51.     (b range 1 10)
  52.     (c range 1 10)
  53.     (= (+ (* 100 a) (* 10 b) c)
  54.        (+ (fact 1) (fact b) (fact c)))))
  55. (newline)
  56.  
  57. (display
  58.   (list-of (list p i e)
  59.     (p range 1 10)
  60.     (i range 1 10)
  61.     (e range 1 10)
  62.     (= (+ (sqrt (+ (* 10 p) i)) e)
  63.        (sqrt (+ (* 100 p) (* 10 i) e))))
  64. )
  65. (newline)
Success #stdin #stdout 0.11s 51152KB
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(59 12)
((1 4 5))
((1 6 9))
https://ideone.com/DEm8X7
language:
Scheme (guile 2.2.4)
created:
5 years ago
visibility:
public

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