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Groups > comp.lang.c > #138532
| From | David Brown <david.brown@hesbynett.no> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Big integers |
| Date | 2018-12-05 14:35 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <pu8k6m$tva$1@dont-email.me> (permalink) |
| References | <YfuND.286973$lKb.275890@fx15.am4> <g6oqspF2giqU1@mid.individual.net> <L3PND.252067$Z%1.51148@fx16.am4> |
On 05/12/18 12:58, Bart wrote:
> On 05/12/2018 02:19, Ian Collins wrote:
>> On 05/12/2018 01:17, Bart wrote:
>
>>> * Keeps use of typedefs to a minimum (used to declare some aliases for
>>> int32_t etc, and to make the one struct used, into a type)
>>
>> Looks tidy, but I would keep those aliases out of the header - the _t
>> names were partly picked to minimise the risk of name clashes.
>
> You mean, /I/ shouldn't use int32 so that someone else can?
You should not use "int32" in a /header/, in case other people want to
use it. What you do in the /implementation/ is up to you.
To most of us, there is absolutely no point in having types like "int32"
as typedefs for "int32_t" - it is an entirely negative thing. It merely
introduces a non-standard name with no functionality, severing to
confuse, complicate and irritate. So /users/ of your library are not
remotely interested in having a type "int32" defined here.
I realise that you think "int32_t" is so hideously ugly that you don't
want to use it in your own code, and prefer a typedef to "int32". I
can't say I can comprehend that attitude, but I can appreciate that this
is your opinion. So if you want to use "int32" in your implementation
code, go ahead. The emphasis in the C code should be what suits /you/
best, while the emphasis in the header file is what suits /others/ best.
I would actually severely question the choice of types here altogether.
I would say more natural types would be :
typedef struct {
uint_least32_t * ptr;
unsigned int ndigits;
bool minus;
} BigInt;
If you want C90 compatibility, use:
#if UINT_MAX < 0xffffffff
#error The implementation requires at least 32-bit unsigned int
#endif
typedef struct {
unsigned int * ptr;
unsigned int ndigits;
int minus;
} BigInt;
As for the library itself, I have a few suggestions which you may or may
not use. It is entirely up to you - it depends on how you want to use
the library.
First, in any API you should strive to minimise extra functions.
"bn_print" is useful - "bn_println" is not.
Secondly, be very careful to be clear about ownership of allocated
resources. It is not clear from the functional API that BigInt types
hold resources and need freed by the user. In particular, the "bn_free"
function is listed as paired with the "bn_tostring" function - it gives
the impression that you use "bn_free" to free the memory allocated by
the "bn_tostring" function, which is clearly not the case.
With a big number library, you have a choice of bases to use. Base 10
makes printing easier - but it makes calculations a good deal less
efficient. You have to choose which makes sense for you. It is also
more common to use little-endian ordering - again, it is easier to be
efficient.
You could also separate the count of the blocks allocated from the
number of digits used. This can make it easier to do in-place
operations (like "x += y") with fewer allocations and copies. And you
really want in-place operations for a library like this:
a = bn_add(a, b);
will be slow an leaky, while:
bn_add_to(&a, b);
would be faster and safe.
Finally, I would want a "small number optimisation" feature - a fixed
size of data, perhaps 4 uint32_t or a single uint64_t - within the
BigInt struct itself. Numbers that are small enough to be stored there
would be there, and be very much faster to use.
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Big integers Bart <bc@freeuk.com> - 2018-12-04 12:17 +0000
Re: Big integers fir <profesor.fir@gmail.com> - 2018-12-04 05:58 -0800
Re: Big integers Chad <cdalten@gmail.com> - 2018-12-04 08:22 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-04 17:04 +0000
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-04 17:19 +0000
Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-04 08:38 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-04 17:35 +0000
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-04 18:13 +0000
Re: Big integers "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-04 10:50 -0800
Re: Big integers Rosario19 <Ros@invalid.invalid> - 2018-12-06 17:56 +0100
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-04 10:22 -0800
Re: Big integers Eli the Bearded <*@eli.users.panix.com> - 2018-12-04 18:58 +0000
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-04 11:32 -0800
Re: Big integers Eli the Bearded <*@eli.users.panix.com> - 2018-12-04 22:45 +0000
Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-04 14:57 -0800
Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-04 12:14 -0800
Re: Big integers chris.m.thomasson.1@gmail.com - 2018-12-04 16:58 -0800
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 03:14 +0000
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:27 -0800
Re: Big integers Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-04 20:03 -0500
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:25 -0800
Re: Big integers jacob navia <jacob@jacob.remcomp.fr> - 2018-12-04 23:45 +0100
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-04 23:29 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 00:30 +0000
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:28 -0800
Re: Big integers Jens Stuckelberger <Jens_Stuckelberger@nowhere.net> - 2018-12-05 17:50 +0000
Re: Big integers jacobnavia <jacob@jacob.remcomp.fr> - 2018-12-05 20:03 +0100
Re: Big integers Keith Thompson <kst-u@mib.org> - 2018-12-05 13:46 -0800
Re: Big integers jacobnavia <jacob@jacob.remcomp.fr> - 2018-12-06 06:41 +0100
Re: Big integers Keith Thompson <kst-u@mib.org> - 2018-12-05 22:40 -0800
Re: Big integers "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-04 09:08 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-04 19:41 +0000
Re: Big integers "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2018-12-04 12:00 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-08 11:28 +0000
Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-05 15:19 +1300
Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 11:58 +0000
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-05 14:35 +0100
Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 14:35 +0000
Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-05 07:39 -0800
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-05 07:45 -0800
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 17:51 +0000
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-05 22:19 +0100
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 14:55 -0800
Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-05 15:19 -0800
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-05 16:13 -0800
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-06 09:35 +0100
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-07 14:26 -0800
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-07 19:56 -0800
Re: Big integers James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-09 12:01 -0500
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-10 14:47 -0800
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 00:50 +0000
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-10 17:37 -0800
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-14 21:18 -0800
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-05 07:57 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 15:59 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-05 22:59 +0000
Re: Big integers jameskuyper@alumni.caltech.edu - 2018-12-05 15:31 -0800
Re: Big integers Robert Wessel <robertwessel2@yahoo.com> - 2018-12-05 20:03 -0600
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-05 23:42 +0000
Re: Big integers James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-05 20:15 -0500
Re: Big integers Ike Naar <ike@iceland.freeshell.org> - 2018-12-10 07:26 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 18:38 +0000
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-10 19:10 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 21:23 +0000
Re: Big integers Ike Naar <ike@iceland.freeshell.org> - 2018-12-10 22:47 +0000
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-05 22:15 +0100
Re: Big integers Bart <bc@freeuk.com> - 2018-12-06 13:43 +0000
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-06 07:50 -0800
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 15:19 +0000
Re: Big integers luser droog <luser.droog@gmail.com> - 2018-12-10 23:19 -0800
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-11 08:45 +0100
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-11 11:15 +0000
Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-11 04:36 -0800
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-11 14:35 +0100
Re: Modules again (was: Big integers) Bart <bc@freeuk.com> - 2018-12-11 12:53 +0000
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 14:45 +0100
Re: Modules again Bart <bc@freeuk.com> - 2018-12-11 16:08 +0000
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:37 +0100
Re: Modules again Thiago Adams <thiago.adams@gmail.com> - 2018-12-11 08:59 -0800
Re: Modules again Bart <bc@freeuk.com> - 2018-12-11 17:49 +0000
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:44 +0100
Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 18:02 +0000
Re: Modules again Thiago Adams <thiago.adams@gmail.com> - 2018-12-11 10:10 -0800
Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 18:54 +0000
Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 13:14 -0500
Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 18:54 +0000
Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 14:42 -0500
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:54 +0100
Re: Modules again Keith Thompson <kst-u@mib.org> - 2018-12-11 14:53 -0800
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-12 08:24 +0100
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-11 21:51 +0100
Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-11 23:24 +0000
Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 18:44 -0500
Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-11 18:45 -0500
Re: Modules again Jorgen Grahn <grahn+nntp@snipabacken.se> - 2018-12-12 06:39 +0000
Re: Modules again James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-12 07:59 -0500
Re: Modules again mark.bluemel@gmail.com - 2018-12-12 05:43 -0800
Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-12 14:20 +0000
Re: Modules again David Brown <david.brown@hesbynett.no> - 2018-12-12 17:10 +0100
Re: Modules again James Kuyper <jameskuyper@alumni.caltech.edu> - 2018-12-12 13:39 -0800
Re: Modules again scott@slp53.sl.home (Scott Lurndal) - 2018-12-12 14:19 +0000
Re: Modules again Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2018-12-12 10:28 -0500
Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-06 08:10 +1300
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 20:57 +0000
Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-06 10:16 +1300
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-05 23:15 +0000
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-05 23:44 +0000
Re: Big integers Robert Wessel <robertwessel2@yahoo.com> - 2018-12-05 02:51 -0600
Re: Big integers antispam@math.uni.wroc.pl - 2018-12-07 15:26 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-07 16:27 +0000
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-07 16:36 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-07 17:01 +0000
Re: Big integers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2018-12-07 17:55 +0000
Re: Big integers antispam@math.uni.wroc.pl - 2018-12-07 19:26 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-07 21:39 +0000
Re: Big integers Ian Collins <ian-news@hotmail.com> - 2018-12-08 10:51 +1300
Re: Big integers Anton Shepelev <anton.txt@gmail.com> - 2018-12-08 00:43 +0300
Re: Big integers Bart <bc@freeuk.com> - 2018-12-08 01:08 +0000
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-08 15:13 +0100
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-08 15:15 +0100
Re: Big integers Bart <bc@freeuk.com> - 2018-12-08 14:48 +0000
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-10 05:10 -0800
Re: Big integers Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2018-12-10 05:22 -0800
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-10 15:27 +0100
Re: Big integers scott@slp53.sl.home (Scott Lurndal) - 2018-12-10 15:59 +0000
Re: Big integers antispam@math.uni.wroc.pl - 2018-12-11 21:14 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 14:56 +0000
Re: Big integers Ike Naar <ike@iceland.freeshell.org> - 2018-12-10 17:46 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 18:24 +0000
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-10 11:12 -0800
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-10 11:23 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-10 21:44 +0000
Re: Big integers Thiago Adams <thiago.adams@gmail.com> - 2018-12-11 10:20 -0800
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-11 13:15 -0800
Re: Big integers Keith Thompson <kst-u@mib.org> - 2018-12-08 12:14 -0800
Re: Big integers David Brown <david.brown@hesbynett.no> - 2018-12-09 13:31 +0100
Re: Big integers "Chris M. Thomasson" <invalid_chris_thomasson@invalid.invalid> - 2018-12-08 15:52 -0800
Re: Big integers Bart <bc@freeuk.com> - 2018-12-16 19:29 +0000
Re: Big integers "Tristan B. Kildaire" <deavmi@disroot.org> - 2018-12-25 12:59 +0000
Re: Big integers Bart <bc@freeuk.com> - 2018-12-25 15:54 +0000
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