Implement unit circle example

`unit_circle.sh` generates a animated GIF of the circle states between
p=1 and p=3.

1 files changed, 39 insertions, 0 deletions

diff --git a/unit_circle.cc b/unit_circle.cc
new file mode 100644
index 0000000..283fb53
--- /dev/null
+++ b/unit_circle.cc
@@ -0,0 +1,39 @@
+#include <imgen.h>
+
+#include <cmath>
+#include <vector>
+#include <algorithm>
+
+int p_norm(double p, int x, int y) {
+	return static_cast<int>(std::nearbyint(
+		std::pow(
+			std::pow(std::abs(x), p) + std::pow(std::abs(y), p),
+			1.0 / p
+		)
+	));
+}
+
+void generate_p_unit_circle(
+	const double lower,
+	const double upper,
+	const double epsilon
+) {
+	for ( double p = lower; p < upper + epsilon; p = p + epsilon ) {
+		imgen::write_ppm(
+			"unit_circle_" + std::to_string(p) + ".ppm",
+			128,
+			128,
+			[p](std::ptrdiff_t x, std::ptrdiff_t y) -> imgen::color {
+				if ( p_norm(p, x, y) <= 32 ) {
+					return imgen::black();
+				} else {
+					return imgen::white();
+				}
+			}
+		);
+	}
+}
+
+int main(int, char*[]) {
+	generate_p_unit_circle(1.0, 3.0, 0.05);
+}