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Groups > comp.lang.c > #76070

Re: Objective C

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Objective C
Date 2015-11-15 02:06 +0000
Organization A noiseless patient Spider
Message-ID <87y4e0uibn.fsf@bsb.me.uk> (permalink)
References (7 earlier) <49e74554-a5a2-4441-9676-2e59118b1079@googlegroups.com> <ln1tbsns69.fsf@kst-u.example.com> <40031c30-7a37-495b-990c-af271a82aa2d@googlegroups.com> <lnwptkm9q3.fsf@kst-u.example.com> <55613c36-e3f3-4b26-b654-4b543e1acfdb@googlegroups.com>

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

> On Saturday, November 14, 2015 at 11:39:56 PM UTC, Keith Thompson wrote:
>> Malcolm McLean <malcolm.mclean5@btinternet.com> writes:
>> 
>> How do you convert a float to int?
>> 
>>     float f = 42.0;
>>     int i = f;
>> 
>> How do you print a human-readable representation of a float value?
>> 
>>     printf("%f\n", f);
>> 
>> How are strict aliasing / effective type rules relevant to any of this?
>> My point is that Alla, and other novice C programmers, don't need to
>> worry about any of that.  (I rarely worry about it myself.)
>> 
> If you're content to say they work by magic, then fair enough.
> But if you want to understand what's going on, you have to
> explain it in terms of reinterpretation of bits, or aliasing.

I thought the point you were making was to query how one can implement a
conversion from one set of bits (the representation of a float that you
suggested) to an int value in C without falling foul of the various type
and aliasing rules.  If that indeed was your question, one answer is to
use bit fields with unsigned int type.  The answer can be calculated
from those integers by a simple but laborious bit of code.

But given this more recent answer, I'm not sure what you point is
anymore.  You can explain what's going on in the conversion and printing
above without making any reference to C at all, so there's no obvious
link to C rules about reinterpretation and aliasing.

-- 
Ben.

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Thread

Objective C Alla _ <modelling.data@gmail.com> - 2015-11-10 09:10 -0800
  Re: Objective C "Rick C. Hodgin" <rick.c.hodgin@gmail.com> - 2015-11-10 09:16 -0800
  Re: Objective C Richard Heathfield <rjh@cpax.org.uk> - 2015-11-10 17:17 +0000
  Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-10 09:32 -0800
    Re: Objective C Mark Storkamp <mstorkamp@yahoo.com> - 2015-11-10 11:38 -0600
  Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-10 12:36 -0500
    Re: Objective C Alla _ <modelling.data@gmail.com> - 2015-11-10 11:15 -0800
      Re: Objective C Richard Heathfield <rjh@cpax.org.uk> - 2015-11-10 21:51 +0000
        Re: Objective C Alla _ <modelling.data@gmail.com> - 2015-11-10 23:13 -0800
      Re: Objective C supercat@casperkitty.com - 2015-11-13 16:01 -0800
        Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-14 01:07 +0000
          Re: Objective C supercat@casperkitty.com - 2015-11-14 06:26 -0800
            Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-14 22:22 +0000
              Re: Objective C supercat@casperkitty.com - 2015-11-14 15:46 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 01:47 +0000
                Re: Objective C BartC <bc@freeuk.com> - 2015-11-15 10:43 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-15 13:19 -0800
            Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 15:43 -0800
            Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-15 23:50 +0100
              Re: Objective C gazelle@shell.xmission.com (Kenny McCormack) - 2015-11-16 00:05 +0000
              Re: Objective C supercat@casperkitty.com - 2015-11-15 19:10 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-16 09:11 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-16 11:57 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-16 20:38 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-16 13:20 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-16 22:28 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-16 15:33 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-16 15:56 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 01:43 +0000
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-17 01:21 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-16 18:11 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-16 20:12 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-19 00:59 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-18 22:46 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-19 14:25 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-19 07:58 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-19 22:13 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-19 15:29 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 08:44 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-17 01:26 +0000
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-16 21:48 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-16 20:27 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-17 13:58 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-17 12:28 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-18 13:00 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-18 12:31 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-18 16:43 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-18 15:57 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-19 19:09 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-19 19:05 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-20 15:00 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-20 15:30 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 17:11 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-22 15:53 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-23 13:51 -0600
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-24 12:00 +0000
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-17 10:26 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-17 06:20 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-17 16:41 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-17 12:08 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-17 16:27 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-17 14:55 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-18 13:59 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-18 13:06 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-24 14:24 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-24 15:11 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-26 17:02 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-27 07:26 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-18 21:56 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 02:17 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-22 07:16 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-26 17:11 -0600
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-22 19:09 +0000
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-17 23:28 -0600
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-18 15:33 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-18 23:06 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-19 09:12 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-19 09:25 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-19 21:06 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-20 13:49 -0800
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-21 05:01 -0600
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-21 05:09 -0600
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-21 03:31 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-21 17:43 -0600
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-21 16:00 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 01:12 -0600
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-27 16:42 +0000
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-27 12:38 -0500
                Re: Objective C supercat@casperkitty.com - 2015-11-27 11:09 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-21 19:06 -0500
                Re: Objective C supercat@casperkitty.com - 2015-11-21 17:00 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-22 14:44 +0000
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 01:55 -0600
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-22 00:03 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-22 10:18 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 03:21 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-22 10:53 -0500
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-22 20:28 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-22 18:52 -0800
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-23 11:58 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-23 15:24 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-23 09:46 -0500
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-23 08:13 -0800
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-23 12:04 -0500
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-23 11:52 -0600
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 16:05 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-24 09:09 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-12-08 08:48 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-12-08 10:40 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-12-09 12:34 -0800
                Re: Objective C supercat@casperkitty.com - 2015-12-08 10:50 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-12-09 12:42 -0800
                Re: Objective C supercat@casperkitty.com - 2015-12-09 13:38 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-12-10 19:54 +0000
                Re: Objective C David Thompson <dave.thompson2@verizon.net> - 2015-12-06 08:02 -0500
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-22 14:36 -0800
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-23 00:41 -0600
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 07:39 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-22 14:23 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-17 10:24 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-18 15:40 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-20 16:02 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-21 15:53 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-21 08:58 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-22 22:14 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 03:39 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-23 13:24 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-26 09:39 -0800
                Re: Objective C Robert Wessel <robertwessel2@yahoo.com> - 2015-11-26 13:16 -0600
                Re: Objective C supercat@casperkitty.com - 2015-11-26 12:25 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 14:34 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-26 12:39 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-27 16:43 +0000
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-27 09:29 -0800
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 14:18 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-23 22:35 +0000
                Re: Objective C James Kuyper <jameskuyper@verizon.net> - 2015-11-23 17:40 -0500
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-24 05:35 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-25 12:15 -0800
                Re: Objective C glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-11-25 22:49 +0000
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-27 16:44 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 14:03 -0800
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-29 09:29 +0000
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-22 19:01 +0000
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-23 07:31 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-23 07:43 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-23 08:17 -0800
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-23 17:34 +0100
                Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-23 22:02 +0000
                Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-24 10:12 +0100
                Re: Objective C Tim Rentsch <txr@alumni.caltech.edu> - 2015-11-27 08:39 -0800
          Re: Objective C Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-11-14 18:24 +0000
        Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 12:23 -0800
          Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 12:36 -0800
            Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 13:13 -0800
              Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 14:04 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 14:15 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 14:29 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-14 15:39 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-14 16:37 -0800
                Re: Objective C Ian Collins <ian-news@hotmail.com> - 2015-11-15 13:46 +1300
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 02:06 +0000
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-15 03:25 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 12:56 +0000
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-15 07:53 -0600
                Re: Objective C Stephen Sprunk <stephen@sprunk.org> - 2015-11-15 07:19 -0600
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-15 13:29 +0000
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-15 10:56 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-15 14:35 -0800
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-15 16:52 -0800
                Re: Objective C supercat@casperkitty.com - 2015-11-15 19:49 -0800
                Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-16 11:02 +0000
                Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-16 10:36 -0800
                Re: Objective C David Thompson <dave.thompson2@verizon.net> - 2015-12-06 08:03 -0500
                Re: Objective C Melzzzzz <mel@zzzzz.com> - 2015-11-16 02:01 +0100
                Re: Objective C supercat@casperkitty.com - 2015-11-15 19:34 -0800
                Re: Objective C Chad <cdalten@gmail.com> - 2015-11-15 19:54 -0800
                Re: Objective C raltbos@xs4all.nl (Richard Bos) - 2015-11-17 22:36 +0000
                Re: Objective C supercat@casperkitty.com - 2015-11-17 15:27 -0800
                Re: Objective C Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-11-17 21:15 -0800
          Re: Objective C Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-11-14 22:08 +0000
      Re: Objective C fir <profesor.fir@gmail.com> - 2015-11-27 14:36 -0800
  Re: Objective C David Brown <david.brown@hesbynett.no> - 2015-11-10 19:03 +0100
    Re: Objective C Keith Thompson <kst-u@mib.org> - 2015-11-10 10:50 -0800

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