----- Original Message ----- From: "joel falcou" <joel.falcou@lri.fr> To: <boost@lists.boost.org> Sent: Saturday, October 09, 2010 8:16 AM Subject: Re: [boost] [Review] Boost.Ratio
On 09/10/10 00:16, vicente.botet wrote:
The idea is to specialize mpl arithmetic operation for ratio. As Ratio is not a Integral Constants we need to define a new on, let me call it Rational Constant. What could be the requirements for a Rational Constant?
Expression Type Complexity r::tag rational_c_tag Constant time. r::value_type A boost::rational<integral_type> type Constant time. r::num An integral constant expression Constant time. r::den An integral constant expression Constant time. r::type Rational Constant Constant time. r::value_type c = r.value() R::value_type Constant time.
Expression Semantics r::tag r's tag type; n::tag::value is n's conversion rank. r::num The value of the numerator integral constant. r::den The value of the denominator integral constant. r::type 'is_equivalent'<r::type,r>::value == true. c=r.value() c.numerator() * r::den == c.denominator() * r::num.
I could implemented this, but before doing it I will want to heard the maintainers of MPL about this feature and if they will accept to include it in his library.
Oh the idea was not to include ratio in MPL but just make ratio expose the needed inner type so you could drop any ratio type into mpl operations.
As far as I know this the mpl operations could not be compatible with tha Rational constant concept. Please give a depth description of what are you seen that I don't see.
Respect to fusion adaptors, I don't see what can be done. Could detal a little bit more:
Basically, soemtime I needed to acces the numerator or denominator through fusion::at_c or apply fusion::for_each on them.
int n = fusion::at_c<0>( some_ratio );
I can make the adaptor if you want, it's like 20 lines. It can sit in an optional file (much like ratio_io) and be included only if needed.
Please post these lines and I will see if this can be intergrated into Boost.Ratio. Best, Vicente