Groups > comp.os.linux.development.apps > #451

Re: cast double to short problem

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From	Grant Edwards <invalid@invalid.invalid>
Newsgroups	comp.os.linux.development.apps
Subject	Re: cast double to short problem
Date	Wed, 7 Mar 2012 20:13:53 +0000 (UTC)
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On 2012-03-07, Ersek, Laszlo <lacos@caesar.elte.hu> wrote:
>
>> Ah, there's your problem: expecting to get 3.  You should expect to
>> get either 2 or 3.  And you do. :)
>
> He should get the same result both times.

Yes.  He should.  My point is that he shouldn't expect to.

His code should not be written to depend on either (int)(0.3 * 10.0)
== 2 or on (int)(0.3 * 10.0) == 3.

> - The floating point environment is the same.
> - dval starts out the same (as in "object representation").
> - 10 (int) is converted to double the same way (with exact value).
> - Both double multiplications happen with the same operands (as in 
> "object representation").
> - Initialization of (~ simple assignment to) a double does not change the 
> double product (as in "object representation").
> - Conversion to short is the same (truncated toward zero).

I agree: I think it should produce the same result in both cases.

-- 
Grant Edwards               grant.b.edwards        Yow! I'm using my X-RAY
                                  at               VISION to obtain a rare
                              gmail.com            glimpse of the INNER
                                                   WORKINGS of this POTATO!!

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Thread

cast double to short problem Bill M <wpmccormick@just_about_everywhere.com> - 2012-03-06 16:52 -0600
  Re: cast double to short problem Grant Edwards <invalid@invalid.invalid> - 2012-03-06 23:21 +0000
    Re: cast double to short problem Bill M <wpmccormick@just_about_everywhere.com> - 2012-03-06 17:36 -0600
      Re: cast double to short problem Grant Edwards <invalid@invalid.invalid> - 2012-03-07 00:30 +0000
        Re: cast double to short problem Noob <root@127.0.0.1> - 2012-03-07 11:17 +0100
          Re: cast double to short problem Grant Edwards <invalid@invalid.invalid> - 2012-03-07 15:23 +0000
    Re: cast double to short problem "Ersek, Laszlo" <lacos@caesar.elte.hu> - 2012-03-07 19:33 +0100
      Re: cast double to short problem Grant Edwards <invalid@invalid.invalid> - 2012-03-07 20:13 +0000
        Re: cast double to short problem Bill M <wpmccormick@just_about_everywhere.com> - 2012-03-08 11:45 -0600

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