
Boost : 
From: Michael Fawcett (michael.fawcett_at_[hidden])
Date: 20080326 18:12:26
On Wed, Mar 26, 2008 at 4:36 PM, John Femiani <JOHN.FEMIANI_at_[hidden]> wrote:
>
> IMHO the core need from a point library is the concepts, not the models,
> because there are so many different welltuned geometry libraries that
> exist, and the idea is that boost _algorithms_ work on any "point",
> rather than that boost have a great point class (those are easy).
I agree, what do you think of this extremely simple starting point?
The names definitely need work.
template <typename T>
struct CompileTimePointConcept {
void constraints() {
typedef typename at_c<typename T::element_seq, 0>::type x_type;
typedef typename at_c<typename T::element_seq, 1>::type y_type;
x_type &x = get<0>(value);
y_type &y = get<1>(value);
}
private:
T value;
};
template <typename T, int N>
struct CompileTimePointConcept<T[N]> {
void constraints() {
T &x = get<0>(value);
T &y = get<1>(value);
}
private:
T value[N];
};
template <typename T>
struct RuntimeIndexablePointConcept {
void constraints() {
typedef typename at_c<typename T::element_seq, 0>::type x_type;
typedef typename at_c<typename T::element_seq, 1>::type y_type;
BOOST_MPL_ASSERT((is_same<x_type, y_type>));
int i = 0;
x_type &x = value[i];
y_type &y = value[i + 1];
}
private:
T value;
};
template <typename T, int N>
struct RuntimeIndexablePointConcept<T[N]> {
void constraints() {
int i = 0;
T &x = value[i];
T &y = value[i + 1];
}
private:
T value[N];
};
As you can see, one behaves very much like a tuple, the other like an
array. T::element_seq could be an mpl::vector or maybe Fusion could
help adapt legacy structs easier (I've not played with Fusion yet).
What else would a PointConcept need? "Point" almost feels like a
misnomer since it implies much more than most algorithms require...
Michael Fawcett
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk