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From: Ian Collins <ian-news@hotmail.com>
Newsgroups: comp.lang.c++
Subject: Re: Integer promotions, conversions, coercions and templates :(
Date: Thu, 09 Jun 2011 10:22:26 +1200
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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);

> I made arg n a type T just to
> avoid fld and n being different unsigned integer types.

fld?

> Is CheckBit correct? If not, can it be corrected? Can it be improved?

Test it!

-- 
Ian Collins