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// Example of using the GeographicLib::DST class
#include <iostream>
#include <exception>
#include <vector>
#include <GeographicLib/Math.hpp>
#include <GeographicLib/DST.hpp>
using namespace std;
using namespace GeographicLib;
class sawtooth {
private:
double _a;
public:
sawtooth(double a) : _a(a) {}
// only called for x in (0, pi/2]. DST assumes function is periodic, period
// 2*pi, is odd about 0, and is even about pi/2.
double operator()(double x) const { return _a * x; }
};
int main() {
try {
sawtooth f(Math::pi()/4);
DST dst;
int N = 5, K = 2*N;
vector<double> tx(N), txa(2*N);
dst.reset(N);
dst.transform(f, tx.data());
cout << "Transform of sawtooth based on " << N << " points\n"
<< "approx 1, -1/9, 1/25, -1/49, ...\n";
for (int i = 0; i < min(K,N); ++i) {
int j = (2*i+1)*(2*i+1)*(1-((i&1)<<1));
cout << i << " " << tx[i] << " " << tx[i]*j << "\n";
}
tx.resize(2*N);
dst.refine(f, tx.data());
cout << "Add another " << N << " points\n";
for (int i = 0; i < min(K,2*N); ++i) {
int j = (2*i+1)*(2*i+1)*(1-((i&1)<<1));
cout << i << " " << tx[i] << " " << tx[i]*j << "\n";
}
dst.reset(2*N);
dst.transform(f, txa.data());
cout << "Retransform of sawtooth based on " << 2*N << " points\n";
for (int i = 0; i < min(K,2*N); ++i) {
int j = (2*i+1)*(2*i+1)*(1-((i&1)<<1));
cout << i << " " << txa[i] << " " << txa[i]*j << "\n";
}
cout << "Table of values and integral\n";
for (int i = 0; i <= K; ++i) {
double x = i*Math::pi()/(2*K), sinx = sin(x), cosx = cos(x);
cout << x << " " << f(x) << " "
<< DST::eval(sinx, cosx, txa.data(), 2*N) << " "
<< DST::integral(sinx, cosx, txa.data(), 2*N) << "\n";
}
}
catch (const exception& e) {
cerr << "Caught exception: " << e.what() << "\n";
return 1;
}
}
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