[macstl-dev] Re: Question about sized booleans

[Ilya Lipovsky]

>
>
>>> Also, how to properly use your select function?
>>
>>
>>
>> The signature looks similar to this:
>>
>> valarray <T> select (const valarray <bool>& boolexpr, const valarray 
>> <T>& trueexpr, const valarray <T>& falseexpr);
>>
>> And it will chunk i.e. optimize using Altivec whenever the boolexpr 
>> has the same element size (and in SSE, similar base element) as the 
>> trueexpr and falseexpr e.g.
>>
>> valarray <float> a, b;
>> valarray <float> c = select (a < b, a, b);    // is a naive 
>> implementation of min (a, b)
>>
>> You can replace any of the parameters with scalar "constants" (except 
>> for all of the constants), so
>>
>> c = select (true, a, b);
>> c = select (a < b, 1.0f, b);
>> c = select (a < b, a, 1.0f);
>> c = select (true, 1.0f, b);
>> c = select (true, a, 1.0f);
>> c = select (a < b, 1.0f, 2.0f);
>>
>> will all work and the constants act as if they are a valarray 
>> containing just that constant. (I say "constant" because you can 
>> substitute a scalar variable instead but I wanted the examples to be 
>> clearer.)
>
>
> So that means that I was using your "select(...)" correctly. Now I 
> will be investigating other venues of resolution. My compiler gives me 
> this:
>
> error: cannot convert `stdext::valarray<float>' to `fd_set*' for 
> argument `2' to `int select(int, fd_set*, fd_set*, fd_set*, timeval*)'
>
> even though I don't include any system headers.


Due to shortage of time (can't waste more than 2 hours on the silly 
issue) I propose a workaround: how about if we rename "select" into 
"sel?" Seems work fine for me. Even though "select" sounds more 
understandable, "sel" is shorter to type. Btw, we never invoke 
"exponent" -- only "exp." So it doesn't go against any conventions.

What's your take on the proposition?

-Ilya