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54 lines
1.8 KiB
Racket
54 lines
1.8 KiB
Racket
#lang racket/base
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(require racket/list)
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(provide (all-defined-out))
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(define (base-base digit-str
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#:offset [offset 0]
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#:min-width [min-width #f])
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(define digits (list->vector (string->list digit-str)))
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(define len (vector-length digits))
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(values
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(λ (num)
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(let loop ([num (+ num offset)] [acc null])
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(if (zero? num)
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(list->string
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(if (and min-width (< (length acc) min-width))
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(append (make-list (- min-width (length acc)) (vector-ref digits 0)) acc)
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acc))
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(let* ([r (modulo num len)]
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[q (quotient (- num r) len)])
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(loop q (cons (vector-ref digits r) acc))))))
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(λ (str)
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(define digit-table (for/hash ([c (in-string digit-str)]
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[i (in-naturals)])
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(values c i)))
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(- (for/sum ([c (in-list (reverse (string->list str)))]
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[i (in-naturals)])
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(* (hash-ref digit-table c) (expt len i))) offset))))
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(define-values (base62 unbase62)
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(base-base "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"))
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(define-values (base-readable unbase-readable)
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(base-base "abcdefghjkmpqrtuvwxy2346789"))
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(define-values (zbase32 unzbase32)
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(base-base "ybndrfg8ejkmcpqxot1uwisza345h769"))
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(define-values (rfc4648 unrfc4648)
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(base-base "abcdefghijklmnopqrstuvwxyz234567"))
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(define-values (no-vowel un-no-vowel)
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(base-base "bcdfghjklmnpqrstvwxz0123456789"))
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(define-values (base32-uc unbase32-uc)
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(base-base "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
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(define-values (base-uc unbase-uc)
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(base-base "ABCDEFGHIJKLMNOPQRSTUVWXYZ"))
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(module+ test
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(require rackunit)
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(check-equal? (base62 10234) "2F4")
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(check-equal? (unbase62 "2F4") 10234)) |