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Groups > comp.lang.c > #24053

Re: Restricted unsigned integer range would have been better?

Message-ID	<501935C7.5D52@mindspring.com> (permalink)
Date	2012-08-01 09:57 -0400
From	pete <pfiland@mindspring.com>
Organization	PF
Newsgroups	comp.lang.c
Subject	Re: Restricted unsigned integer range would have been better?
References	(9 earlier) <5018AE22.152C@mindspring.com> <P4Odncjoya6Oe4XNnZ2dnUVZ8iSdnZ2d@lyse.net> <0.41a5266becbe1d48f128.20120801125152BST.87r4rq4yp3.fsf@bsb.me.uk> <50191E78.CDB@mindspring.com> <0.837a8fa3b84a81796f37.20120801142215BST.87lihy4uig.fsf@bsb.me.uk>

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Ben Bacarisse wrote:
> 
> pete <pfiland@mindspring.com> writes:
> 
> > Ben Bacarisse wrote:
> <snip>
> >> > On 01/08/2012 06:18, pete wrote:
> >> >> Philip Lantz wrote:
> <snip>
> >> >>>    5. while (*s != '\0')
> >> >>>           n = n * 10 + (*s - '0');
> <snip>
> >> >> If n is of type int and also not negative,
> >> >> then you could write without having to use parentheses
> >> >>      n = n * 10 - '0' + *s;
> >> >> with no possibility of overflow.
> >>
> >> I don't understand that.
> >> Did you mean "and also unsigned" rather than
> >> "and also not negative"?
> >
> > No.
> > It reminded me of a line from a toy atoi
> > that I once wrote as an exercise.
> 
> Ah!  You meant that the parentheses can be removed without causing an
> otherwise avoidable overflow, I think.

Yes. That's what I meant.
Thank you.

> Both versions can overflow, but
> the "bad" version (n = n * 10 + *s - '0')
> can cause a needless overflow.

I also think I should change the condition my loop from
        while (isdigit(*nptr)) {
to 
        while (*nptr != '\0') {
similar to what Philip Lantz had.
I think that the spirit of atoi
is that it is supposed to be a simple function,
which is only to be used 
when it is known that the input won't cause any problems.

-- 
pete

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Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-23 01:32 -0600
Re: Restricted unsigned integer range would have been better? "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-07-23 01:45 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 00:19 -0600
Re: Restricted unsigned integer range would have been better? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-24 11:25 +0100
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 16:22 -0600
Re: Restricted unsigned integer range would have been better? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-07-25 01:53 +0100
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 21:43 -0600
Re: Restricted unsigned integer range would have been better? "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2012-07-24 16:29 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 21:53 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-24 23:24 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-25 01:12 -0600
Re: Restricted unsigned integer range would have been better? Nobody <nobody@nowhere.com> - 2012-07-23 10:37 +0100
Re: Restricted unsigned integer range would have been better? Andre <lodwig@pathme.de> - 2012-07-23 11:46 +0200
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-23 11:33 +0100
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-23 23:48 -0600
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-24 10:43 +0100
Re: Restricted unsigned integer range would have been better? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-07-24 02:58 -0700
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-24 12:04 +0100
Re: Restricted unsigned integer range would have been better? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-07-24 05:32 -0700
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-24 14:20 +0100
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-24 18:41 +0100
Re: Restricted unsigned integer range would have been better? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-07-24 12:37 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 16:15 -0600
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 16:05 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-24 23:28 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-25 01:13 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-25 01:26 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-25 05:43 -0600
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-07-24 15:10 +0200
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-24 16:23 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-24 23:40 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-25 01:32 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-25 01:29 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-25 05:45 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-25 12:35 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-26 00:12 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-26 01:42 -0700
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-07-25 09:31 +0200
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-25 06:28 -0600
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-07-25 16:28 +0200
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-25 17:17 +0100
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-07-26 12:07 +0200
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-26 14:06 +0100
Re: Restricted unsigned integer range would have been better? James Kuyper <jameskuyper@verizon.net> - 2012-07-26 09:45 -0400
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-07-30 09:01 +0200
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-26 00:09 -0600
Re: Restricted unsigned integer range would have been better? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-07-26 00:52 -0700
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-07-26 20:35 -0400
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-26 22:35 -0600
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-07-27 09:19 -0400
Re: Restricted unsigned integer range would have been better? Les Cargill <lcargill99@comcast.com> - 2012-07-27 12:51 -0500
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-27 16:19 -0700
Re: Restricted unsigned integer range would have been better? Les Cargill <lcargill99@comcast.com> - 2012-07-27 18:47 -0500
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-07-30 09:10 +0200
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-07-31 17:26 -1000
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-08-01 00:18 -0400
Re: Restricted unsigned integer range would have been better? "io_x" <a@b.c.invalid> - 2012-08-01 10:19 +0200
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-08-01 10:09 +0200
Re: Restricted unsigned integer range would have been better? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-01 12:51 +0100
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-08-01 08:18 -0400
Re: Restricted unsigned integer range would have been better? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-01 14:22 +0100
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-08-01 09:57 -0400
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-08-01 11:35 -0400
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2012-09-07 11:43 -0700
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-09-08 10:13 -0400
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-09-22 23:39 -0700
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-09-22 23:45 -0700
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 13:52 -0800
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 13:45 -0800
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-12-17 19:51 -0500
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-12-28 11:11 -0800
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-29 11:31 -0800
Re: Restricted unsigned integer range would have been better? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2012-12-29 23:59 +0000
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-02 10:01 -0800
Re: Restricted unsigned integer range would have been better? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2013-01-05 12:00 +0200
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2013-01-02 13:07 -0800
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2013-01-03 12:10 -0800
Re: Restricted unsigned integer range would have been better? James Kuyper <jameskuyper@verizon.net> - 2013-01-05 12:26 -0500
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-09-22 23:35 -0700
Re: Restricted unsigned integer range would have been better? Tim Rentsch <txr@alumni.caltech.edu> - 2012-12-17 14:02 -0800
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-08-01 10:06 +0200
Re: Restricted unsigned integer range would have been better? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2012-08-01 12:46 +0100
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-08-02 08:19 -1000
Re: Restricted unsigned integer range would have been better? Philip Lantz <prl@canterey.us> - 2012-08-02 08:17 -1000
Re: Restricted unsigned integer range would have been better? David Brown <david@westcontrol.removethisbit.com> - 2012-08-03 08:04 +0200
Re: Restricted unsigned integer range would have been better? "io_x" <a@b.c.invalid> - 2012-08-03 09:40 +0200
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-27 22:27 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-07-28 01:31 -0700
Re: Restricted unsigned integer range would have been better? "BartC" <bc@freeuk.com> - 2012-07-28 10:52 +0100
Re: Restricted unsigned integer range would have been better? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-07-28 03:31 -0700
Re: Restricted unsigned integer range would have been better? pete <pfiland@mindspring.com> - 2012-07-28 00:05 -0400
Re: Restricted unsigned integer range would have been better? Les Cargill <lcargill99@comcast.com> - 2012-07-27 23:22 -0500
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-07-27 22:35 -0600
Re: Restricted unsigned integer range would have been better? Malcolm McLean <malcolm.mclean5@btinternet.com> - 2012-08-04 08:43 -0700
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-08-04 16:40 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-04 22:58 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-08-04 23:10 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-05 01:16 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-08-05 02:25 -0700
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-05 03:35 -0600
Re: Restricted unsigned integer range would have been better? Keith Thompson <kst-u@mib.org> - 2012-08-05 12:16 -0700
Re: Restricted unsigned integer range would have been better? gazelle@shell.xmission.com (Kenny McCormack) - 2012-08-05 19:56 +0000
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-06 01:12 -0600
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-06 01:07 -0600
Re: Restricted unsigned integer range would have been better? gazelle@shell.xmission.com (Kenny McCormack) - 2012-08-05 13:33 +0000
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-06 01:13 -0600
Re: Restricted unsigned integer range would have been better? "Ansel" <tinker454@trytospammenowloser.com> - 2012-08-04 22:54 -0600

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