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  1. ; tri-48
  2.  
  3. (define (isqrt n)
  4.   (if (not (and (positive? n) (integer? n)))
  5.       (error 'isqrt "must be positive integer")
  6.       (let loop ((x n))
  7.         (let ((y (quotient (+ x (quotient n x)) 2)))
  8.           (if (< y x) (loop y) x)))))
  9.  
  10. (define (square? n)
  11.   (let ((root (isqrt n)))
  12.     (= (* root root) n)))
  13.  
  14. (define (squares n)
  15.   (let loop ((x (isqrt n)) (y 0) (zs '()))
  16.     (cond ((< x y) zs)
  17.           ((< (+ (* x x) (* y y)) n) (loop x (+ y 1) zs))
  18.           ((< n (+ (* x x) (* y y))) (loop (- x 1) y zs))
  19.           (else (loop (- x 1) (+ y 1) (cons (list x y) zs))))))
  20.  
  21. (display (squares (* 48 48))) (newline)
  22.  
  23. (define (tri n)
  24.   (let loop ((a 1))
  25.     (let ((c (+ (* a a) (* n n))))
  26.       (when (square? c)
  27.         (display (sort (list a (isqrt c) n) <))
  28.         (newline)))
  29.     (when (< a 1000) (loop (+ a 1)))))
  30.  
  31. (tri 48)
Success #stdin #stdout 0.09s 43488KB
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stdin
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Standard input is empty
stdout
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((48 0))
(14 48 50)
(20 48 52)
(36 48 60)
(48 55 73)
(48 64 80)
(48 90 102)
(48 140 148)
(48 189 195)
(48 286 290)
(48 575 577)
https://ideone.com/yX11Fm
language:
Scheme (guile 2.2.4)
created:
6 years ago
visibility:
public

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