From: Mark H Weaver <mhw@netris.org>
To: Freeman Gilmore <freeman.gilmore@gmail.com>
Cc: guile-user@gnu.org
Subject: Re: Unicode numeric value
Date: Mon, 17 Dec 2018 13:42:17 -0500 [thread overview]
Message-ID: <87bm5kxae3.fsf@netris.org> (raw)
In-Reply-To: <CAM=7=uS81i53bRy3r1q_RDtxvEmhgt3n2bC54_Gtveb3cxxQtw@mail.gmail.com> (Freeman Gilmore's message of "Sun, 16 Dec 2018 06:24:08 -0500")
Hi,
Freeman Gilmore <freeman.gilmore@gmail.com> writes:
> On Sun, Dec 16, 2018 at 3:15 AM Mark H Weaver <mhw@netris.org> wrote:
>
> Freeman Gilmore <freeman.gilmore@gmail.com> writes:
>
> > I am looking for a procedure that will read the numeric value, field 8, of
> > an Unicode numeric character. Has anyone written this procedure or know
> > where I can find it?
>
> The 'r7rs-wip' branch of the Guile git repository contains a procedure
> that does this, with a lookup table derived from Unicode 6.3.0.
>
> https://git.savannah.gnu.org/cgit/guile.git/tree/module/scheme/char.scm?h=r7rs-wip
>
> The file is written as an R7RS library form, which won't work on current
> releases of Guile, but for now you could simply extract the
> 'digit-value' procedure from it, provided that you preserve the
> copyright notice.
>
> Mark
>
> Thank you Mark:
>
> That is only half the battle, let me explain. I do not want to read
> the standard Unicode table. I want to directly read field 8 of a
> numeric character in the privet use area of the Unicode.
>
> This is not part of scheme. The other half, I need to finger out how
> to put the numeric values in field 8 for the characters I want to use.
If the mapping from code points to numeric values is static, then you
could simply modify the lookup table in the code I suggested above.
If the mapping is dynamic, then you'll need a different strategy. One
simple approach would be to use a hash table mapping from characters to
digit values:
(define digit-value-table (make-hash-table))
(define (set-digit-value! char value)
(hashv-set! digit-value-table char value))
(define (digit-value char)
(hashv-ref digit-value-table char #f))
If the range of relevant code points is small enough, another approach
would be to use a vector:
(define private-code-point-start #xE000)
(define private-code-point-end #xF900)
(define (code-point-in-range? cp)
(<= private-code-point-start
cp
private-code-point-end))
(define digit-value-table
(make-vector (- private-code-point-end
private-code-point-start)
#f))
(define (set-digit-value! char value)
(let ((cp (char->integer char)))
(unless (code-point-in-range? cp)
(error "set-digit-value!: code point out of range:" cp))
(vector-set! digit-value-table
(- cp private-code-point-start)
value)))
(define (digit-value char)
(let ((cp (char->integer char)))
(and (code-point-in-range? cp)
(vector-ref digit-value-table
(- cp private-code-point-start)))))
For a more compact representation, you could use a SRFI-4 homogeneous
numeric vector instead, although you'd need to designate a special
numeric value to represent "not a digit".
Regards,
Mark
next prev parent reply other threads:[~2018-12-17 18:42 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-16 4:31 Unicode numeric value Freeman Gilmore
2018-12-16 6:11 ` John Cowan
2018-12-16 8:14 ` Mark H Weaver
2018-12-16 11:24 ` Freeman Gilmore
2018-12-17 18:42 ` Mark H Weaver [this message]
2018-12-17 18:52 ` Mark H Weaver
2019-01-05 1:07 ` Freeman Gilmore
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