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  1. ; i'm embarrassed
  2.  
  3. (define (take n xs)
  4.   (let loop ((n n) (xs xs) (ys '()))
  5.     (if (or (zero? n) (null? xs))
  6.         (reverse ys)
  7.         (loop (- n 1) (cdr xs)
  8.               (cons (car xs) ys)))))
  9.  
  10. (define (drop n xs)
  11.   (let loop ((n n) (xs xs))
  12.     (if (or (zero? n) (null? xs)) xs
  13.       (loop (- n 1) (cdr xs)))))
  14.  
  15. (define (digits n . args)
  16.   (let ((b (if (null? args) 10 (car args))))
  17.     (let loop ((n n) (d '()))
  18.       (if (zero? n) d
  19.           (loop (quotient n b)
  20.                 (cons (modulo n b) d))))))
  21.  
  22. (define (dollar x)
  23.   (define (commas n)
  24.     (let ((xs (reverse (map number->string (digits n)))))
  25.       (let loop ((xs (drop 3 xs)) (zs (reverse (take 3 xs))))
  26.         (if (null? xs) (apply string-append zs)
  27.           (loop (drop 3 xs) (append (reverse (take 3 xs)) (list ",") zs))))))
  28.   (define (zero n)
  29.     (if (zero? n) "00"
  30.       (if (< n 10) (string-append "0" (number->string n))
  31.         (number->string n))))
  32.   (let* ((n (inexact->exact (round (* x 100))))
  33.          (dollars (quotient n 100))
  34.          (cents (modulo n 100)))
  35.     (string-append "$" (commas dollars) "." (zero cents))))
  36.  
  37. (display (dollar 1234567.9999)) (newline)
Success #stdin #stdout 0.02s 8800KB
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$1,234,568.00
https://ideone.com/xg7nFo
language:
Scheme (guile 2.2.4)
created:
7 years ago
visibility:
public

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