Re: [Boost-users] [proto] Question on grammar and operator overloading

Subject: Re: [Boost-users] [proto] Question on grammar and operator overloading
From: Hal Finkel (half_at_[hidden])
Date: 2009-10-06 16:04:43

Eric,

I'm trying this option, but I can't get it to work correctly (the
compiler does not find the operator overloads when I require
boost::is_array to be "true"). If you uncomment the appropriate 3 lines
in the grammar definition in the attached source file, you'll see what I
mean.

Thanks again,
Hal

On Tue, 2009-10-06 at 12:32 -0400, Eric Niebler wrote:
> Hal Finkel wrote:
> > Eric,
> > 
> > Thank you, I'll use the predicate approach for now. I like the idea of
> > using an array base because I have a lot of existing C and C++ code
> > which treats complex numbers as a 2 element array, and accesses the
> > members using the [] operator. I think this is common in
> > high-performance scientific codes. I'm afraid doing it another way could
> > lead to the generation of a large number of conditionals which the
> > optimizer can't figure out how to eliminate (meaning (idx ? imag() :
> > real()), I'd have to test this on several platforms), or the
> > introduction of a lot of casts.
> 
> If you're going that route, you could just drop boost::array and use 
> native arrays:
> 
>    proto::terminal< double[2] >::type
> 
> Then your grammar changes to:
> 
>    proto::and_<
>      proto::terminal<_>,
>      proto::if_<boost::is_array<proto::_value>()>
>    >
> 
> HTH,
>