Lissajous, showing floating point arithmetic

apps/lissajous/lissajous.c

@@ -0,0 +1,118 @@
+#define USE_MAIN
+#include "uvm32_target.h"
+
+// https://github.com/shastro/CodeGolf-Lissajous/blob/master/lissa.c
+// https://github.com/nicbk/donut-embedded/blob/ad8061ece9a2c156694c39af12f109ea6778da52/donut.c#L57
+
+#define PI 3.14159265358979323846  // First 21 digits of pi
+
+void movecursor(int x, int y) {
+    print("\033[");
+    printdec(y);
+    print(";");
+    printdec(x);
+    print("f");
+}
+
+void sleep(uint32_t ms) {
+    uint32_t start = millis();
+    while (millis() < start + ms) {
+        yield();
+    }
+}
+
+// Absolute value function for doubles
+double abs_c(double x) {
+    if (x < 0) {
+        return -x;
+    } else {
+        return x;
+    }
+}
+
+// Recursive factorial capable of calculating a max of approximately 10^18 in size
+unsigned long long fac(unsigned char x) {
+    if (x == 0) {
+        return 1;
+    } else {
+        return x * fac(x - 1);
+    }
+}
+
+// Exponential function
+// Ignores edge cases such as indeterminate forms for simplicity
+double pow_c(double x, unsigned char n) {
+    if (n == 0) {
+        return 1;
+    } else {
+        double product = x;
+
+        for (int i = 1; i < n; ++i) {
+            product *= x;
+        }
+
+        return product;
+    }
+}
+
+// MacLaurin series approximation of sin(x) from -PI/2 to PI/2
+// with eight terms, and extended to the domain of all
+// real numbers with modular arithmetic.
+double sin(double x) {
+    double translation = 0;
+    if (x > -PI / 2) {
+        translation = (int)((x + PI / 2) / PI);
+    } else {
+        translation = (int)((x - PI / 2) / PI);
+    }
+
+    x -= PI * translation;
+    if ((int)abs_c(translation) % 2 == 1) {
+        x = -x;
+    }
+
+    double sum = 0;
+
+    for (int i = 0; i < 9; ++i) {
+        sum += pow_c(-1, i) * pow_c(x, 2 * i + 1) / fac(2 * i + 1);
+    }
+
+    return sum;
+}
+
+// cos(x) function derived from sin(x)
+double cos(double x) {
+    return sin(PI / 2 - x);
+}
+
+void main(void) {
+    int freq1 = 45;
+    int freq2 = 90;
+
+    for (int i = 0; i < 300; i++) {
+        putc('\n');
+    }
+    print("\033[H");  // Cursor at Corner of Screen
+
+    float x = 0;
+    float y = 0;
+    float angle = 0;
+    float beta = 0.0;
+
+    while (1) {
+        uint32_t framestart = millis();
+        for (angle = 0; angle < 2 * PI; angle += 0.15) {
+            movecursor(x, y);
+            x = 40 * cos(freq1 * angle + beta) + 60;
+            y = 20 * sin(freq2 * angle) + 30;
+            print("#");
+        }
+        // wait for next frame
+        while (millis() < framestart + 20) {
+            yield();
+        }
+        beta += 0.05;
+
+        print("\033[2J");
+    }
+}