1 #ifndef LIB2GEOM_SEEN_POLY_H
2 #define LIB2GEOM_SEEN_POLY_H
3 #include <assert.h>
4 #include <vector>
5 #include <iostream>
6 #include <algorithm>
7 #include <complex>
8 #include <2geom/utils.h>
10 namespace Geom {
12 class Poly : public std::vector<double>{
13 public:
14 // coeff; // sum x^i*coeff[i]
16 //unsigned size() const { return coeff.size();}
17 unsigned degree() const { return size()-1;}
19 //double operator[](const int i) const { return (*this)[i];}
20 //double& operator[](const int i) { return (*this)[i];}
22 Poly operator+(const Poly& p) const {
23 Poly result;
24 const unsigned out_size = std::max(size(), p.size());
25 const unsigned min_size = std::min(size(), p.size());
26 //result.reserve(out_size);
28 for(unsigned i = 0; i < min_size; i++) {
29 result.push_back((*this)[i] + p[i]);
30 }
31 for(unsigned i = min_size; i < size(); i++)
32 result.push_back((*this)[i]);
33 for(unsigned i = min_size; i < p.size(); i++)
34 result.push_back(p[i]);
35 assert(result.size() == out_size);
36 return result;
37 }
38 Poly operator-(const Poly& p) const {
39 Poly result;
40 const unsigned out_size = std::max(size(), p.size());
41 const unsigned min_size = std::min(size(), p.size());
42 result.reserve(out_size);
44 for(unsigned i = 0; i < min_size; i++) {
45 result.push_back((*this)[i] - p[i]);
46 }
47 for(unsigned i = min_size; i < size(); i++)
48 result.push_back((*this)[i]);
49 for(unsigned i = min_size; i < p.size(); i++)
50 result.push_back(-p[i]);
51 assert(result.size() == out_size);
52 return result;
53 }
54 Poly operator-=(const Poly& p) {
55 const unsigned out_size = std::max(size(), p.size());
56 const unsigned min_size = std::min(size(), p.size());
57 resize(out_size);
59 for(unsigned i = 0; i < min_size; i++) {
60 (*this)[i] -= p[i];
61 }
62 for(unsigned i = min_size; i < out_size; i++)
63 (*this)[i] = -p[i];
64 return *this;
65 }
66 Poly operator-(const double k) const {
67 Poly result;
68 const unsigned out_size = size();
69 result.reserve(out_size);
71 for(unsigned i = 0; i < out_size; i++) {
72 result.push_back((*this)[i]);
73 }
74 result[0] -= k;
75 return result;
76 }
77 Poly operator-() const {
78 Poly result;
79 result.resize(size());
81 for(unsigned i = 0; i < size(); i++) {
82 result[i] = -(*this)[i];
83 }
84 return result;
85 }
86 Poly operator*(const double p) const {
87 Poly result;
88 const unsigned out_size = size();
89 result.reserve(out_size);
91 for(unsigned i = 0; i < out_size; i++) {
92 result.push_back((*this)[i]*p);
93 }
94 assert(result.size() == out_size);
95 return result;
96 }
97 // equivalent to multiply by x^terms, negative terms are disallowed
98 Poly shifted(unsigned const terms) const {
99 Poly result;
100 size_type const out_size = size() + terms;
101 result.reserve(out_size);
103 result.resize(terms, 0.0);
104 result.insert(result.end(), this->begin(), this->end());
106 assert(result.size() == out_size);
107 return result;
108 }
109 Poly operator*(const Poly& p) const;
111 template <typename T>
112 T eval(T x) const {
113 T r = 0;
114 for(int k = size()-1; k >= 0; k--) {
115 r = r*x + T((*this)[k]);
116 }
117 return r;
118 }
120 template <typename T>
121 T operator()(T t) const { return (T)eval(t);}
123 void normalize();
125 void monicify();
126 Poly() {}
127 Poly(const Poly& p) : std::vector<double>(p) {}
128 Poly(const double a) {push_back(a);}
130 public:
131 template <class T, class U>
132 void val_and_deriv(T x, U &pd) const {
133 pd[0] = back();
134 int nc = size() - 1;
135 int nd = pd.size() - 1;
136 for(unsigned j = 1; j < pd.size(); j++)
137 pd[j] = 0.0;
138 for(int i = nc -1; i >= 0; i--) {
139 int nnd = std::min(nd, nc-i);
140 for(int j = nnd; j >= 1; j--)
141 pd[j] = pd[j]*x + operator[](i);
142 pd[0] = pd[0]*x + operator[](i);
143 }
144 double cnst = 1;
145 for(int i = 2; i <= nd; i++) {
146 cnst *= i;
147 pd[i] *= cnst;
148 }
149 }
151 static Poly linear(double ax, double b) {
152 Poly p;
153 p.push_back(b);
154 p.push_back(ax);
155 return p;
156 }
157 };
159 inline Poly operator*(double a, Poly const & b) { return b * a;}
161 Poly integral(Poly const & p);
162 Poly derivative(Poly const & p);
163 Poly divide_out_root(Poly const & p, double x);
164 Poly compose(Poly const & a, Poly const & b);
165 Poly divide(Poly const &a, Poly const &b, Poly &r);
166 Poly gcd(Poly const &a, Poly const &b, const double tol=1e-10);
168 /*** solve(Poly p)
169 * find all p.degree() roots of p.
170 * This function can take a long time with suitably crafted polynomials, but in practice it should be fast. Should we provide special forms for degree() <= 4?
171 */
172 std::vector<std::complex<double> > solve(const Poly & p);
174 /*** solve_reals(Poly p)
175 * find all real solutions to Poly p.
176 * currently we just use solve and pick out the suitably real looking values, there may be a better algorithm.
177 */
178 std::vector<double> solve_reals(const Poly & p);
179 double polish_root(Poly const & p, double guess, double tol);
181 inline std::ostream &operator<< (std::ostream &out_file, const Poly &in_poly) {
182 if(in_poly.size() == 0)
183 out_file << "0";
184 else {
185 for(int i = (int)in_poly.size()-1; i >= 0; --i) {
186 if(i == 1) {
187 out_file << "" << in_poly[i] << "*x";
188 out_file << " + ";
189 } else if(i) {
190 out_file << "" << in_poly[i] << "*x^" << i;
191 out_file << " + ";
192 } else
193 out_file << in_poly[i];
195 }
196 }
197 return out_file;
198 }
200 } // namespace Geom
202 #endif //LIB2GEOM_SEEN_POLY_H
204 /*
205 Local Variables:
206 mode:c++
207 c-file-style:"stroustrup"
208 c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
209 indent-tabs-mode:nil
210 fill-column:99
211 End:
212 */
213 // vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:encoding=utf-8:textwidth=99 :