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Groups > comp.lang.c > #55515

Re: solution allocation of memory and composite numbers

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: solution allocation of memory and composite numbers
Date 2014-12-27 21:55 +0000
Organization A noiseless patient Spider
Message-ID <87k31cg3kr.fsf@bsb.me.uk> (permalink)
References (5 earlier) <Q8Gmw.179333$td3.38698@fx34.am4> <87tx0kekzh.fsf@bsb.me.uk> <vfJmw.313270$td6.168835@fx30.am4> <877fxegj8f.fsf@bsb.me.uk> <1ecde9d0-2198-4d06-a324-222af341db20@googlegroups.com>

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Malcolm McLean <malcolm.mclean5@btinternet.com> writes:

> On Friday, December 26, 2014 10:05:29 PM UTC, Ben Bacarisse wrote:
>> Richard Heathfield <invalid@see.sig.invalid> writes:
>> 
>> > Ben Bacarisse wrote:
>> 
>> >>   if (scanf("%d", &number) == 1)
>> 
>> Do you think this is "astoundingly difficult"?
>>
> Tempting, but it's undefined behaviour if fed with a huge integer like
> "10000000000000000000000000000000000000", in C89 at least. No sane
> implementation would crash out, but it's not clear how it should
> behave.
> The worst feature is that
>
> scanf("%d, %d\n", &a, &b)
>
> when fed with
>
> 100,
> 200
>
> will still convert 2 fields.

Why is that not the best feature of scanf?

To be less cryptic, I think you missed the point.  In this context the
instructor gets to choose the input format and what should and should
not be handled and how.  The instructor can set things up so that
students make headway with a whole range of things (functions,
variables, arithmetic, control flow and so on) without input being a
huge barrier.

What would you suggest in place of

  if (scanf("%d", &number) == 1)

in an introductory C course?

-- 
Ben.

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Thread

solution allocation of memory and composite numbers Dexterr <dejangru@gmail.com> - 2014-12-24 05:52 -0800
  Re: solution allocation of memory and composite numbers Dexterr <dejangru@gmail.com> - 2014-12-24 05:55 -0800
    Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-24 06:41 -0800
      Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-24 20:16 +0000
        Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-24 12:39 -0800
          Re: solution allocation of memory and composite numbers Richard Heathfield <invalid@see.sig.invalid> - 2014-12-24 21:22 +0000
            Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-24 22:33 +0000
              Re: solution allocation of memory and composite numbers Richard Heathfield <invalid@see.sig.invalid> - 2014-12-25 00:54 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-24 18:38 -0800
                Re: solution allocation of memory and composite numbers Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-25 12:07 +0100
                Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-26 22:05 +0000
                Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-26 22:33 +0000
                Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-27 22:08 +0000
                Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-27 23:28 +0000
                Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-29 18:34 +0000
                Re: solution allocation of memory and composite numbers raltbos@xs4all.nl (Richard Bos) - 2014-12-30 19:23 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-26 15:43 -0800
                Re: solution allocation of memory and composite numbers Keith Thompson <kst-u@mib.org> - 2014-12-26 15:59 -0800
                Re: solution allocation of memory and composite numbers Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-27 14:45 +0100
                Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-27 21:55 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-27 14:07 -0800
                Re: solution allocation of memory and composite numbers Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-27 23:44 +0100
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-27 15:49 -0800
                Re: solution allocation of memory and composite numbers Keith Thompson <kst-u@mib.org> - 2014-12-27 21:52 -0800
                Re: solution allocation of memory and composite numbers Vincenzo Mercuri <nomail@yahoo.it> - 2014-12-28 15:54 +0100
                Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-28 00:03 +0000
                Re: solution allocation of memory and composite numbers Keith Thompson <kst-u@mib.org> - 2014-12-26 17:13 -0800
                Re: solution allocation of memory and composite numbers Geoff <geoff@invalid.invalid> - 2014-12-27 10:23 -0800
                Re: solution allocation of memory and composite numbers Stephen Sprunk <stephen@sprunk.org> - 2014-12-27 13:03 -0600
                Re: solution allocation of memory and composite numbers Keith Thompson <kst-u@mib.org> - 2014-12-27 12:24 -0800
                Re: solution allocation of memory and composite numbers Keith Thompson <kst-u@mib.org> - 2014-12-27 12:23 -0800
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-27 13:31 -0800
                Re: solution allocation of memory and composite numbers Öö Tiib <ootiib@hot.ee> - 2014-12-27 18:42 -0800
                Re: solution allocation of memory and composite numbers Keith Thompson <kst-u@mib.org> - 2014-12-27 22:07 -0800
                Re: solution allocation of memory and composite numbers raltbos@xs4all.nl (Richard Bos) - 2014-12-30 19:26 +0000
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-30 20:01 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-30 12:18 -0800
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-30 21:15 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-30 13:49 -0800
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-30 22:03 +0000
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-30 23:57 +0000
                Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-30 22:35 +0000
                Re: solution allocation of memory and composite numbers Dr Nick <nospam-4@temporary-address.org.uk> - 2014-12-31 12:24 +0000
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-31 17:08 +0000
                Re: solution allocation of memory and composite numbers Dr Nick <nospam-4@temporary-address.org.uk> - 2014-12-31 17:37 +0000
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-30 20:09 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-30 12:24 -0800
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2014-12-30 21:28 +0000
                Re: solution allocation of memory and composite numbers Malcolm McLean <malcolm.mclean5@btinternet.com> - 2014-12-30 13:53 -0800
                Re: solution allocation of memory and composite numbers Kaz Kylheku <kaz@kylheku.com> - 2015-01-04 02:22 +0000
                Re: solution allocation of memory and composite numbers Xavier Roche <xroche@free.fr.NOSPAM.invalid> - 2014-12-31 13:32 +0100
                Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-27 01:37 +0000
                Re: solution allocation of memory and composite numbers raltbos@xs4all.nl (Richard Bos) - 2014-12-27 12:19 +0000
                Re: solution allocation of memory and composite numbers gazelle@shell.xmission.com (Kenny McCormack) - 2014-12-27 14:39 +0000
          Re: solution allocation of memory and composite numbers Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-12-24 22:29 +0000
    Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-24 15:05 +0000
  Re: solution allocation of memory and composite numbers Richard Heathfield <invalid@see.sig.invalid> - 2014-12-24 16:55 +0000
    iso646.h Noob <root@127.0.0.1> - 2014-12-25 18:26 +0100
      Re: iso646.h Geoff <geoff@invalid.invalid> - 2014-12-25 18:31 -0800
        Re: iso646.h Noob <root@127.0.0.1> - 2014-12-26 18:23 +0100
      Re: iso646.h Keith Thompson <kst-u@mib.org> - 2014-12-25 21:31 -0800
        Re: iso646.h fir <profesor.fir@gmail.com> - 2014-12-26 09:42 -0800
  Re: solution allocation of memory and composite numbers Barry Schwarz <schwarzb@dqel.com> - 2014-12-24 09:06 -0800
  Re: solution allocation of memory and composite numbers Richard Heathfield <invalid@see.sig.invalid> - 2014-12-24 16:59 +0000
  Re: solution allocation of memory and composite numbers BartC <bc@freeuk.com> - 2014-12-24 17:26 +0000
    Re: solution allocation of memory and composite numbers asetofsymbols@gmail.com - 2014-12-24 11:42 -0800

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