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(define-module (text big-numbers)
:use-module ((hnh util) :select (->>))
:use-module (hnh util type)
:export (number->exponential-form
power-of-10?
subscript supscript))
(define (integer-string-ref str n)
(typecheck str string?)
(typecheck n (and exact? integer?))
(->> n
number->string
string->list
(map char->integer)
(map (lambda (x) (- x (char->integer #\0))))
(map (lambda (i) (string-ref str i)))
list->string))
(define (subscript n)
(integer-string-ref "₀₁₂₃₄₅₆₇₈₉" n))
(define (supscript n)
(integer-string-ref "⁰¹²³⁴⁵⁶⁷⁸⁹" n))
;;; Is the number a power of 10?
(define (power-of-10? x)
(integer? (log10 (exact->inexact x))))
(define (number->exponential-form n)
(typecheck n (and exact? integer? power-of-10?))
(string-append "10" (supscript (inexact->exact (round (log10 n))))))
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