Re: [Boost-users] [fusion][mpl::math] generic math operations

22 Jan 2007


      Whoops that should be v[j]

 std::vector
 fft(const std::vector<float>& v)
 {
   std::vector result(v.size(),complex<float>(0,0));
   complex<float> c(0,1);
   for(size_t i=0;i wrote:
...
Hi,
I wanted to try to write a DFT that can take a compile-time data
structure such as the following:
#include 
// v = [1.01 2.01 3.01 4.01 5.01 6.01 7.01]
typedef boost::mpl::math::string_c_to_double<1,'.',0,1>::type D1;
typedef boost::mpl::math::string_c_to_double<2,'.',0,1>::type D2;
typedef boost::mpl::math::string_c_to_double<3,'.',0,1>::type D3;
typedef boost::mpl::math::string_c_to_double<4,'.',0,1>::type D4;
typedef boost::mpl::math::string_c_to_double<5,'.',0,1>::type D5;
typedef boost::mpl::math::string_c_to_double<6,'.',0,1>::type D6;
typedef boost::mpl::math::string_c_to_double<7,'.',0,1>::type D7;
typedef boost::mpl::math::string_c_to_double<8,'.',0,1>::type D8;
typedef boost::fusion::vector VectorType;
and perform the fourier transform at compile time.
The DFT is fairly simple as a for-loop it would look like this:
std::vector
fft(const std::vector<float>& v)
{
  std::vector result(v.size(),complex<float>(0,0));
  complex<float> c(0,1);
  for(size_t i=0;i
To get this algorithm into fusion, I would need a function object for
times, divide, and exp.
Thanks,
Chris
On 1/22/07, Joel de Guzman  wrote:
...
Chris Weed wrote:
...
Hi,
I am interested in combining the fusion and mpl::math libraries, but I
am not sure if they currently support what I want to do.
I want to use generic math operations that can easily switch between
run-time and compile-time. I think this would require writing the
mpl::math functions as "Polymorphic Function Object" as described in
the fusion documentation. I am not sure if there is any mpl::math
documentation that describes this.
It looks like the MPL currently has some math operations that are
strictly meta-functions in boost/mpl/aux_/arithmetic_op.hpp. Are the
any plans to expand these to be functions also?
It would be good to start with some use cases. With use cases,
it's easier to understand what exactly you want to accomplish.
Regards,
--
Joel de Guzman
http://www.boost-consulting.com
http://spirit.sf.net
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