Re: [Boost-users] [Proto] Reducing domain check in operator

Subject: Re: [Boost-users] [Proto] Reducing domain check in operator
From: Eric Niebler (eric_at_[hidden])
Date: 2009-02-26 12:44:15

Joel Falcou wrote:
> But there is a few SIMD operator like for example exponent that can take 
> any vec<T> and return a vec<uint32_t>.
> 
> Currently the operators/functions use the underlying simd expression 
> info to determine their domain, thus leading to problem like :
> 
> exponent(vec<float>) + vec<uint32_t>
> 
> failing to compile cause the domain are not the same.
> 
> Now that I think of it, there is maybe a more elegant solution than 
> hacking the domain check but i'M a bit short of ideas atm.

Strange, you shouldn't be seeing this error in this case. For 
operator(), Proto doesn't enforce domains to match -- the resulting 
expression assumes the domain of the lhs. Consider the following:

   #include <boost/proto/proto.hpp>
   namespace proto = boost::proto;

   template<class E> struct wrap1;
   template<class E> struct wrap2;

   struct domain1 : proto::domain<proto::pod_generator<wrap1> > {};
   struct domain2 : proto::domain<proto::pod_generator<wrap2> > {};

   template<class E> struct wrap1
   {
     BOOST_PROTO_EXTENDS(E, wrap1<E>, domain1)
   };

   template<class E> struct wrap2
   {
     BOOST_PROTO_EXTENDS(E, wrap2<E>, domain2)
   };

   wrap1<proto::terminal<int>::type> _1 = {{1}};
   wrap2<proto::terminal<int>::type> _2 = {{2}};

   int main()
   {
     _1(_2) + _1;     // OK
     // _1(_2) + _2;  // ERROR
   }

_1 and _2 are in different domains, but _1(_2) is allowed and is in the 
domain of _1. That's why the expression "_1(_2) + _1" is permitted, but 
"_1(_2) + _2" is not.

You might have to post your code for us to get to the bottom of this.

-- 
Eric Niebler
BoostPro Computing
http://www.boostpro.com