Change 'lissajous' to draw four curves with different parameters. Als…

…o use more 'const'.

lissajous.c

@@ -14,8 +14,9 @@ int main(int argc, char * const argv[])
 {
    int opt;
    double xc, yc;
+   double h4, w4;
    double maxx, maxy;
-   const double scale = 40.0; /* Plotter units per mm */
+   double side;
 
    while ((opt = getopt(argc, argv, "no:p:s:t:v:")) != -1) {
       switch (opt) {
@@ -45,14 +46,22 @@ int main(int argc, char * const argv[])
    xc = maxx / 2.0;
    yc = maxy / 2.0;
 
-   /* Draw axes */
+   h4 = maxy / 4.0;
+   w4 = maxx / 4.0;
+
+   side = maxy / 3.0;
+
+   /* Split page into quarters */
    moveto(0.0, yc);
    lineto(maxx, yc);
    moveto(xc, 0.0);
    lineto(xc, maxy);
 
-   /* Draw a simple Lissajous curve */
-   lissajous(xc, yc, 150.0 * scale, 5.0, 6.0, 0.0, 144);
+   /* Draw four simple Lissajous curves */
+   lissajous(w4, h4, side, 1.0, 3.0, 0.0, 144);
+   lissajous(xc + w4, h4, side, 5.0, 6.0, 0.0, 144);
+   lissajous(w4, yc + h4, side, 3.0, 5.0, 0.0, 144);
+   lissajous(xc + w4, yc + h4, side, 7.0, 9.0, 0.0, 144);
 
    plotend();
 
@@ -62,23 +71,20 @@ int main(int argc, char * const argv[])
 
 void lissajous(const double x0, const double y0, const double side, const double f1, const double f2, const double theta, const int npts)
 {
-   double t;
-   double t1, t2;
    const double delta = (2.0 * M_PI) / (double)npts;
    const double sintheta = sin(theta);
    const double costheta = cos(theta);
-   double x, y;
    const double r = side / 2.0;
    int i;
 
    for (i = 0; i <= npts; i++) {
-      t = (double)i * delta;
+      const double t = (double)i * delta;
 
-      t1 = t * f1;
-      t2 = t * f2;
+      const double t1 = t * f1;
+      const double t2 = t * f2;
 
-      x = (r * cos(t1) * costheta) - (r * sin(t2) * sintheta);
-      y = (r * cos(t1) * sintheta) + (r * sin(t2) * costheta);
+      const double x = (r * cos(t1) * costheta) - (r * sin(t2) * sintheta);
+      const double y = (r * cos(t1) * sintheta) + (r * sin(t2) * costheta);
 
       if (i == 0)
          moveto(x0 + x, y0 + y);