On 7/17/05, Cromwell Enage <sponage@yahoo.com> wrote: <snip>
The algorithm behind string_c_to_double is not very efficient, so if anyone has a better idea for an implementation, feel free to contribute :)
string_c_to_double looks interesting, perhaps I can use the underlying mechanisms to implement big_integral (which currently takes too many resources to compile, so "not very efficent" is better in this case).
I think the implementation of divide_double_double is a better pattern to follow. It uses a minimum of template instantiations internally, but a pletorum of compile time constants. From my experience, this is much faster compile-time wise than the opposite. Ideally I would like to employ the same technique in string_c_to_double.
On the upside, this implementation uses a 61 bit mantissa, so it is possible to utilize the full mantissa without rounding when calculating e.g. sine. This is done using
boost::metamath::detail::plus_double_double<a,b>::type
boost::metamath::detail::times_double_double<a,b>::type
boost::metamath::detail::divides_double_double<a,b>::type
Would an MPL inner namespace be more appropriate? Say, boost::mpl::aux::double::plus<>, boost::mpl::aux::double::times, etc.
Maybe.
The user should then deal with rounding before returning the final value: boost::metamath::detail::round<a>::type; or boost::metamath::detail::cutoff<a>::type; if no rounding is wanted.
Would it be more practical to pass two arguments to each metafunction? Users don't always want to round to the nearest integer; e.g. for trigonometric apps one might need to round to the nearest PI/8.
Sorry. Bad explanation of what rounding means in this context: Rounding and cutoff here means fitting a 61 bit mantissa into a 52 bit mantissa by taking the 53'rd bit of the mantissa into account (rounding) or not (cutoff) Regards, Peder
The source is available from the vault: http://boost-sandbox.sourceforge.net/vault/ <metamath.zip>
Cool, I'll study it further when I get the chance.
Cromwell D. Enage
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