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

24 Jan 2007

      I don't think this is what he means by 8.24 fixed-point.
I think he is looking for representing a number by 8 bits to the left
of the decimal, and 24 bits after the decimal, thus creating a special
32-bit number format.

I suspect you could use this library to do what you want, but I think
you would need a way to convert the MPL::Math floating-point
representation to your representation. It has been a while since I
looked at the code, but I recall that MPL::Math is essentially an
implementation of IEEE floating-point representation in a templated
class.

Chris

On 1/24/07, Cromwell Enage  wrote:
...
--- Michael Marcin wrote:
...
I hadn't heard of MPL.Math before...
I was actually looking for a way the other day of
computing a fixed-point sin lookup table at
compile-time using Taylor series approximation for
a fixed-point class I have templated on magnitude
and fractional bit count.  I ended up getting lost
and wrote a small program to generate a table and
copy & pasted the output into a source file for
the fixed-point precision I was using at present.
It seems that it would be nice to be able to
generate a new table for say 8.24 fixed-point
without needed to rerun an external tool.
#include <iostream>
#include 
#include 
#include 
using namespace boost;
using namespace mpl;
using namespace math;
int main()
{
    sine >::type
        your_answer;
// The runtime_cast function template
    // converts the internal representation
    // to the template argument type
    // for readability.
    std::cout
     << runtime_cast<double>(your_answer)
     << std::endl;
return 0;
}
...
Does this seem like the sort of thing MPL.Math
could help with?
You can look at the sine.cpp example program and see
for yourself.  As for the sine metafunction
implementation, the Taylor series is actually built
using a combination of Boost.Preprocessor macros and
intermediary typedefs instead of template recursion.
...
Thanks,
No problem.
...
Michael Marcin
Cromwell D. Enage
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Re: [Boost-users] [fusion][mpl::math] generic math operations

Chris Weed