dc(1) bugs

CK nibbana at gmx.us
Wed Jan 13 11:49:17 UTC 2016


Original posting to freebsd-questions ...

FreeBSD-9.3 dc(1)

These appear to be bugs to me, but please verify if possible:

#####
FIRST
#####
$ dc -xe '50k16o16i.1vp'
0
$ dc -xe '50k10o16i.1vp'
0
$ dc -xe '50k10o10i.1vp'
[0].31622776601683793319988935444327185337195551393252

This should be telling dc(1):

a) scale is 50 (in decimal) digits.
b) output in base16, base10, and base10 respectively.
c) input will be in base16, base16, and base10 respectively.
d) take the square root, and print it to the display.

Of course, the 3rd example above is correct, but the first 2?  Why 0?

######
SECOND
######
$ dc -xe '50k16o16i.4 2^p'
[0].0A
$ dc -xe '50k16o16i.0Avp'
[0].2C572B0D5A1443EC508B9E24D8DF392750959EE138

This should be telling dc(1):

a) scale is 50 (in decimal) digits.
b) output in base16, input is now base16.
c) square "0.4", and print it to the display (result=0.0A).
d) take the square-root of "0.0A", and print it to the display.

Of course, the square-root of a squared number should result in
the orginal number.  But, this is not happening.

#####
THIRD
#####
$ dc -xe '50k16o16i.4 2^p'
[0].0A
$ dc -xe '50k16o16i.40 2^p'
[0].1000
$ dc -xe '50k16o16i.400 2^p'
[0].10000
$ dc -xe '50k16o16i.4000 2^p'
[0].1000000

dc(1) is supposed to be precise in the digits it calculates, but here?
Something is not right about these results, or so it appears to me.

######
FOURTH
######
$ dc -xe '50k16o16i.1vp'
0
$ dc -xe '50k16o16i.10vp'
[0].3EB4F9D9B6D094C33D38373D38777A7D9233A1B0FB
$ dc -xe '50k16o16i.100vp'
[0].3FBE55183CA5ADC8B39B27C6258E4C7E64338B909F
$ dc -xe '50k16o16i.1000vp'
[0].400000000000000000000000000000000000000000

Checking the result of the THIRD example, dc(1) is not outputting to the
scale specified, and despite having all a scale of 50, they are all giving
different results with inputs having a scale of only 1/2/3/4;
Something seems broken to me.

--

GNU's dc(1) is broken too:

Wow!  Great!  Thanks!  I really needed a calculator
to do squares and square-roots of hexadecimal fractions,
and I use FreeBSD, but their dc(1) is broken too ...

http://lists.freebsd.org/pipermail/freebsd-questions/2016-January/269999.html
http://lists.freebsd.org/pipermail/freebsd-bugs/2016-January/065825.html

I was a little depressed in writing, sorry :)
But I am so happy if I can find a working dc(1).
Supposedly, it was the first utility, predating
even UNIX.  A modern computer should have a working
calculator - at least, I think so.  Thank you so much
for your reply, I have some encryption-related software
that depends on it.

> On Tuesday 12 January 2016 23:05:41 CK wrote:
>
> > dc (GNU bc 1.06.95) 1.3.95
> >
> > $ dc -e '50k16o16i.4vp'
> > [0].727C9716FFB764D594A519C0252BE9AE6D00DC9192
> >
> > This is not a 50-digit scale.
>
> It is a 50 digit scale base 10 which is of course shorter base 16.
>
> > $ dc -e '50k16o16i.727C9716FFB764D594A519C0252BE9AE6D00DC9192 2^p'
> > [0].333333333333333333333333333333333325CC2DCA
> >
> > This is not even close to being the original number: 0.4.
>
> This appears to be true.   I'll investigate why the algorithm is wrong.
>
> --Phil



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