1 #include <2geom/sbasis-poly.h>
3 namespace Geom{
5 /** Changes the basis of p to be sbasis.
6 \param p the Monomial basis polynomial
7 \returns the Symmetric basis polynomial
9 This algorithm is horribly slow and numerically terrible. Only for testing.
10 */
11 SBasis poly_to_sbasis(Poly const & p) {
12 SBasis x = Linear(0, 1);
13 SBasis r;
15 for(int i = p.size()-1; i >= 0; i--) {
16 r = SBasis(Linear(p[i], p[i])) + multiply(x, r);
17 }
18 r.normalize();
19 return r;
21 }
23 /** Changes the basis of p to be monomial.
24 \param p the Symmetric basis polynomial
25 \returns the Monomial basis polynomial
27 This algorithm is horribly slow and numerically terrible. Only for testing.
28 */
29 Poly sbasis_to_poly(SBasis const & sb) {
30 if(sb.isZero())
31 return Poly();
32 Poly S; // (1-x)x = -1*x^2 + 1*x + 0
33 Poly A, B;
34 B.push_back(0);
35 B.push_back(1);
36 A.push_back(1);
37 A.push_back(-1);
38 S = A*B;
39 Poly r;
41 for(int i = sb.size()-1; i >= 0; i--) {
42 r = S*r + sb[i][0]*A + sb[i][1]*B;
43 }
44 r.normalize();
45 return r;
46 }
48 };
50 /*
51 Local Variables:
52 mode:c++
53 c-file-style:"stroustrup"
54 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
55 indent-tabs-mode:nil
56 fill-column:99
57 End:
58 */
59 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :