Penrose tiling: Difference between revisions

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 * [http://preshing.com/20110831/penrose-tiling-explained/ Deflation explained for Kite and Dart, includes Python code (preshing.com)]
 <br><br>
+=={{header|C++}}==
+{{trans|Nim}}
+<lang cpp>#include <cmath>
+#include <cstdlib>
+#include <fstream>
+#include <iomanip>
+#include <iostream>
+#include <set>
+#include <sstream>
+#include <stack>
+#include <string>
+#include <tuple>
+int main() {
+    std::ofstream out("penrose_tiling.svg");
+    if (!out) {
+        std::cerr << "Cannot open output file.\n";
+        return EXIT_FAILURE;
+    }
+    std::string penrose("[N]++[N]++[N]++[N]++[N]");
+    for (int i = 1; i <= 4; ++i) {
+        std::string next;
+        for (char ch : penrose) {
+            switch (ch) {
+            case 'A':
+                break;
+            case 'M':
+                next += "OA++PA----NA[-OA----MA]++";
+                break;
+            case 'N':
+                next += "+OA--PA[---MA--NA]+";
+                break;
+            case 'O':
+                next += "-MA++NA[+++OA++PA]-";
+                break;
+            case 'P':
+                next += "--OA++++MA[+PA++++NA]--NA";
+                break;
+            default:
+                next += ch;
+                break;
+            }
+        }
+        penrose = std::move(next);
+    }
+    const double r = 30;
+    const double pi5 = 0.628318530717959;
+    double x = r * 8, y = r * 8, theta = pi5;
+    std::set<std::string> svg;
+    std::stack<std::tuple<double, double, double>> stack;
+    for (char ch : penrose) {
+        switch (ch) {
+        case 'A': {
+            double nx = x + r * std::cos(theta);
+            double ny = y + r * std::sin(theta);
+            std::ostringstream line;
+            line << std::fixed << std::setprecision(3) << "<line x1='" << x
+                 << "' y1='" << y << "' x2='" << nx << "' y2='" << ny << "'/>";
+            svg.insert(line.str());
+            x = nx;
+            y = ny;
+        } break;
+        case '+':
+            theta += pi5;
+            break;
+        case '-':
+            theta -= pi5;
+            break;
+        case '[':
+            stack.push({x, y, theta});
+            break;
+        case ']':
+            std::tie(x, y, theta) = stack.top();
+            stack.pop();
+            break;
+        }
+    }
+    out << "<svg xmlns='http://www.w3.org/2000/svg' height='" << r * 16
+        << "' width='" << r * 16 << "'>\n"
+        << "<rect height='100%' width='100%' fill='black'/>\n"
+        << "<g stroke='rgb(255,165,0)'>\n";
+    for (const auto& line : svg)
+        out << line << '\n';
+    out << "</g>\n</svg>\n";
+    return EXIT_SUCCESS;
+}</lang>
+{{out}}
+Writes a file in SVG format similar to that produced by the Perl solution.
 =={{header|Go}}==