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#ifndef LIB2GEOM_STURM_HEADER
#define LIB2GEOM_STURM_HEADER
#include <2geom/poly.h>
#include <2geom/utils.h>
namespace Geom {
class sturm : public std::vector<Poly>{
public:
sturm(Poly const &X) {
push_back(X);
push_back(derivative(X));
Poly Xi = back();
Poly Xim1 = X;
std::cout << "sturm:\n" << Xim1 << std::endl;
std::cout << Xi << std::endl;
while(Xi.size() > 1) {
Poly r;
divide(Xim1, Xi, r);
std::cout << r << std::endl;
assert(r.size() < Xi.size());
Xim1 = Xi;
Xi = -r;
assert(Xim1.size() > Xi.size());
push_back(Xi);
}
}
unsigned count_signs(double t) {
unsigned n_signs = 0;/* Number of sign-changes */
const double big = 1e20; // a number such that practical polys would overflow on evaluation
if(t >= big) {
int old_sign = sgn((*this)[0].back());
for (unsigned i = 1; i < size(); i++) {
int sign = sgn((*this)[i].back());
if (sign != old_sign)
n_signs++;
old_sign = sign;
}
} else {
int old_sign = sgn((*this)[0].eval(t));
for (unsigned i = 1; i < size(); i++) {
int sign = sgn((*this)[i].eval(t));
if (sign != old_sign)
n_signs++;
old_sign = sign;
}
}
return n_signs;
}
unsigned n_roots_between(double l, double r) {
return count_signs(l) - count_signs(r);
}
};
} //namespace Geom
#endif
/*
Local Variables:
mode:c++
c-file-style:"stroustrup"
c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
indent-tabs-mode:nil
fill-column:99
End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :
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