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Groups > comp.lang.c++ > #6471
| From | Ian Collins <ian-news@hotmail.com> |
|---|---|
| Newsgroups | comp.lang.c++ |
| Subject | Re: Integer promotions, conversions, coercions and templates :( |
| Date | 2011-06-09 14:32 +1200 |
| Message-ID | <95apmqFrnrU10@mid.individual.net> (permalink) |
| References | <isorvh$sre$1@dont-email.me> <95ab12FrnrU6@mid.individual.net> <isp36q$7sb$1@dont-email.me> |
On 06/ 9/11 12:13 PM, MikeP wrote:
> Ian Collins wrote:
>> On 06/ 9/11 10:09 AM, MikeP wrote:
>>> I need help (but nevermind that!) templates and the C++ integer
>>> rules are confusing me! (No occifer, I have not been drinking, I am
>>> just dazed and confused by C++ integer rules!).
>>>
>>> // CheckBit
>>> // Checks the status of individual bits of any unsigned integer type.
>>> // Indexing of bits starts at 1, not 0.
>>> // mask can be any unsigned integer type.
>>> // W is the width of the type T.
>>> //
>>> template<typename T, unsigned int W>
>>> bool CheckBit(T& mask, T n)
>>> { // The assertion should be an exception, I know.
>>> Assert((n>= 1)&& (n<= W), "Bit index out of range.")
>>
>> Missing semicolon.
>>
>>> return ((mask& ((T)1)<< (n-((T)1))) != 0);
>>> }
>>>
>>> I wanted to use the appropriate integer type suffix as a template
>>> parameter to use on the 1's (don't know if I needed to though), but
>>> C++ templates won't allow that so I have the casts-to-T all over the
>>> place but I'm not sure if they are necessary.
>>
>> Why don't you just use
>>
>> const T one(1);
>> return (((mask& one)<< (n-one)) != 0);
>
> Adds one move instruction to get '1' into 'one' (which is in a register)
> over the cast-to-T implementation (2 move instructions for 64-bit T), so
> I'd keep the ugly version. Using the suffix would be the way to write
> CheckBit if it wasn't a template:
Poor job on the compiler's part!
The function should optimise down to 0 or 1.
--
Ian Collins
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Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-08 17:09 -0500
Re: Integer promotions, conversions, coercions and templates :( Ian Collins <ian-news@hotmail.com> - 2011-06-09 10:22 +1200
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-08 17:49 -0500
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-08 19:13 -0500
Re: Integer promotions, conversions, coercions and templates :( Ian Collins <ian-news@hotmail.com> - 2011-06-09 14:32 +1200
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-09 07:30 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-09 06:18 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-09 08:45 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-09 06:51 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-09 13:44 -0500
Re: Integer promotions, conversions, coercions and templates :( Ian Collins <ian-news@hotmail.com> - 2011-06-10 07:37 +1200
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-09 15:11 -0500
Re: Integer promotions, conversions, coercions and templates :( Ian Collins <ian-news@hotmail.com> - 2011-06-10 09:09 +1200
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-09 17:15 -0500
Re: Integer promotions, conversions, coercions and templates :( Ian Collins <ian-news@hotmail.com> - 2011-06-10 10:40 +1200
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 05:07 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-10 03:14 -0700
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-10 03:19 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 06:08 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-10 04:32 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 07:14 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-10 05:27 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 07:35 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-10 06:47 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 06:18 -0500
Re: Integer promotions, conversions, coercions and templates :( Ian Collins <ian-news@hotmail.com> - 2011-06-11 08:08 +1200
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 18:41 -0500
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-10 08:11 -0500
Re: Integer promotions, conversions, coercions and templates :( Öö Tiib <ootiib@hot.ee> - 2011-06-09 06:28 -0700
Re: Integer promotions, conversions, coercions and templates :( "MikeP" <mp011011@some.org> - 2011-06-09 08:50 -0500
Re: Integer promotions, conversions, coercions and templates :( (Summary so far) "MikeP" <mp011011@some.org> - 2011-06-10 08:40 -0500
Re: Integer promotions, conversions, coercions and templates :( (Summary so far) Öö Tiib <ootiib@hot.ee> - 2011-06-10 07:14 -0700
Re: Integer promotions, conversions, coercions and templates :( (Summary so far) "MikeP" <mp011011@some.org> - 2011-06-10 09:17 -0500
Re: Integer promotions, conversions, coercions and templates :( (Summary so far)(Corrections and more) "MikeP" <mp011011@some.org> - 2011-06-10 09:14 -0500
Re: Integer promotions, conversions, coercions and templates :( (Results: Generated Code) "MikeP" <mp011011@some.org> - 2011-06-10 12:43 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-14 18:35 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) Ian Collins <ian-news@hotmail.com> - 2011-06-15 12:51 +1200
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-15 08:45 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) Michael DOUBEZ <michael.doubez@free.fr> - 2011-06-15 03:33 -0700
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-15 09:17 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) Michael DOUBEZ <michael.doubez@free.fr> - 2011-06-16 04:17 -0700
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-16 09:45 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) Michael DOUBEZ <michael.doubez@free.fr> - 2011-06-17 01:56 -0700
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-17 07:58 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) Michael DOUBEZ <michael.doubez@free.fr> - 2011-06-17 06:54 -0700
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-17 09:19 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-17 08:17 -0500
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) Michael DOUBEZ <michael.doubez@free.fr> - 2011-06-17 07:33 -0700
Re: Integer promotions, conversions, coercions and templates :( (Conclusion) "MikeP" <mp011011@some.org> - 2011-06-17 09:49 -0500
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