Package: guile;
Message #11 received at 42012 <at> debbugs.gnu.org (full text, mbox):
From: Bengt Richter <bokr <at> bokr.com> To: tomas <at> tuxteam.de Cc: 42012 <at> debbugs.gnu.org Subject: Re: bug#42012: Reference Manual and Docstring on number->string Date: Wed, 24 Jun 2020 05:49:58 +0200
On +2020-06-23 10:34:12 +0200, tomas <at> tuxteam.de wrote:
> On Tue, Jun 23, 2020 at 12:51:23AM +0200, Sebastian Miele wrote:
> > Guile 3.0.3. The reference manual and the docstring of number->string
> > say: "If N is inexact, a radix of 10 will be used." But that is not what
> > happens, e.g.,
> >
> > (let ((x 4.0)) (and (inexact? x) (number->string x 3)))
> >
> > evaluates to "11.0" instead of #f or "4.0". Probably "if RADIX is not
> > supplied, a radix of 10 will be used" is meant.
>
> Confirmed for 3.0.2. At first I thought that the fractional part being
> zero could be significant (as in your example), but
>
> scheme@(guile-user)> (number->string 0.3333333333333333 3)
> $5 = "0.1"
>
> is clearly being done in radix 3, fractional part and all.
>
> Cheers
> -- t
There are some other things that might be mentioned also,
like the characters used by number->string and more surprisingly by string->number :-)
You can try copying the following into ./show-string2num-chars.scm somewhere and chmod 755 it
and try running it, but it will produce one item per line, so it will be handy to let pr format that, like
./show-string2num-chars.scm|pr -t -8|uniq|sed -e 's:^:;;;; :'
Unless your system is different, you should get the table in the comments below.
Since string->number will accept characters past #\z there may be a bug?
See some experiments and speculations below the "BTW" ;-)
--8<---------------cut here---------------start------------->8---
#!/usr/bin/env -S guile --no-auto-compile -e main -s
!#
;;;; show-string2num-chars.scm
(define (main args)
(begin
(let*((chrs255 (cdr (map integer->char (iota 256))))
(ints255 (map (lambda (c) (string->number (string c) 256)) chrs255))
(c2iprs (map (lambda (c i) (cons c i)) chrs255 ints255))
(okprs (filter (lambda (pr) (cdr pr)) c2iprs))
;;
)
(begin
(map (lambda (pr) (format #t "~a=~a\n" (car pr) (cdr pr))) okprs)
;;
))
;;
))
;;;; running this from emacs right after the following line showing the emacs command:
;;;; Esc 1 Esc ! ./show-string2num-chars.scm|pr -t -8|uniq|sed -e 's:^:;;;; :'
;;;; 0=0 9=9 I=18 R=27 Z=35 h=17 p=25 x=33
;;;; 1=1 A=10 J=19 S=28 a=10 i=18 q=26 y=34
;;;; 2=2 B=11 K=20 T=29 b=11 j=19 r=27 z=35
;;;; 3=3 C=12 L=21 U=30 c=12 k=20 s=28 {=36
;;;; 4=4 D=13 M=22 V=31 d=13 l=21 t=29 |=37
;;;; 5=5 E=14 N=23 W=32 e=14 m=22 u=30 }=38
;;;; 6=6 F=15 O=24 X=33 f=15 n=23 v=31 ~=39
;;;; 7=7 G=16 P=25 Y=34 g=16 o=24 w=32 =40
;;;; 8=8 H=17 Q=26
;;;; #\z=35 #\{=36 #\|=37 #\}=38 #\delete=#f
;;;; scheme@(guile-user) [6]>
;;;; BTW
;;;; scheme@(guile-user) [6]> (string-for-each (lambda (c) (format #t "~s=~a " c (string->number (string c) 40))) "z{|}\x7f")(newline)
;;;;
;;;; #\z=35 #\{=36 #\|=37 #\}=38 #\delete=#f
;;;; scheme@(guile-user) [6]>
;;;; it will also apparently happily accept multiple characters z through \x7f and convert them with any radix exceeding
;;;; the largest "digit value
;;;; scheme@(guile-user) [8]> (for-each (lambda (s) (format #t "~s=~a " s (string->number s 1000))) '("0" "1" "10" "z{" "|}" "\x7f")) (newline)
;;;; "0"=0 "1"=1 "10"=1000 "z{"=35036 "|}"=37038 "\x7f"=40
;;;; scheme@(guile-user) [8]>
;;;; the following makes me think possibly the unicode value is taken and masked with 0x7f for ascii and then
;;;; accepted if >= 97 (#\a) (accidentally including > 122 (#\z), only checking for [0-9] and [A-Z] if maked value is less than 97 (#\a)
;;;;scheme@(guile-user) [8]> (for-each (lambda (s) (format #t "~s=~a " s (string->number s 1000))) '("0" "1" "10" "111" "z{" "|}" "\x7f\x80" "\x80\x7f" "\u807e")) (newline)
;;;; "0"=0 "1"=1 "10"=1000 "111"=1001001 "z{"=35036 "|}"=37038 "\x7f\x80"=40041 "\x80\x7f"=#f "聾"=39
;;;; I'll leave it to others to explore further :)
;;;; Note, though, that the inverse -- number->string -- will not accept a radix outide of 2-36:
;;;; scheme@(guile-user) [10]> (number->string (+ (* 34 36) 35) 36)
;;;; $18 = "yz"
;;;; scheme@(guile-user) [10]> (number->string (+ (* 34 36) 35) 40)
;;;; ERROR: In procedure number->string:
;;;; Value out of range 2 to 36: 40
;;;;
;;;; Entering a new prompt. Type `,bt' for a backtrace or `,q' to continue.
;;;; scheme@(guile-user) [11]> (number->string (+ (* 34 36) 35) 37)
;;;; ERROR: In procedure number->string:
;;;; Value out of range 2 to 36: 37
;;;;
--8<---------------cut here---------------end--------------->8---
--
Regards,
Bengt Richter
GNU bug tracking system
Copyright (C) 1999 Darren O. Benham,
1997,2003 nCipher Corporation Ltd,
1994-97 Ian Jackson.