Sierpinski curve: Difference between revisions
Added C++ solution
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Produce a graphical or ASCII-art representation of a [[wp:Sierpiński_curve|Sierpinski curve]] of at least order 3.
=={{header|C++}}==
Output is a file in SVG format. The curve is generated using the Lindenmayer system method.
<lang cpp>// See https://en.wikipedia.org/wiki/Sierpi%C5%84ski_curve#Representation_as_Lindenmayer_system
#include <cmath>
#include <fstream>
#include <iostream>
#include <string>
std::string rewrite(const std::string& s) {
std::string t;
for (char c : s) {
if (c == 'X')
t += "XF+G+XF--F--XF+G+X";
else
t += c;
}
return t;
}
void line(std::ostream& out, double& x, double& y, double length, int angle) {
constexpr double pi = 3.14159265359;
double theta = (pi * angle)/180.0;
x += length * std::cos(theta);
y += length * std::sin(theta);
out << 'L' << x << ',' << y << '\n';
}
void execute(std::ostream& out, const std::string& s, double x, double y,
double length, int angle) {
out << 'M' << x << ',' << y << '\n';
for (char c : s) {
if (c == 'F' || c == 'G')
line(out, x, y, length, angle);
else if (c == '+')
angle = (angle - 45) % 360;
else if (c == '-')
angle = (angle + 45) % 360;
}
}
int main() {
const int size = 545;
const int order = 5;
const double x = 535, y = 5, length = 7;
std::ofstream out("sierpinski_curve.svg");
if (!out) {
std::cerr << "Cannot open output file\n";
return 1;
}
out << "<svg xmlns='http://www.w3.org/2000/svg' width='"
<< size << "' height='" << size << "'>\n";
out << "<rect width='100%' height='100%' fill='white'/>\n";
out << "<path stroke-width='1' stroke='black' fill='none' d='";
std::string s = "F--XF--F--XF";
for (int i = 0; i < order; ++i)
s = rewrite(s);
execute(out, s, x, y, length, 45);
out << "'/>\n</svg>\n";
return 0;
}</lang>
=={{header|Go}}==
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