VitasLALALA

PFont f;
void setup()
{
  size(800, 600);
  frame.setResizable(true);
  f = createFont("Arial",10,true);
}

void draw()
{
  float x1 = -10, x2 = 15, y0;
  float lx, ly, miny, maxy;
  float coef;
  float xsep = width, ysep = height;

  miny = maxy = func(x1);
  for (int i = int(x1); i <= x2; i++)
  {
    float y = func(i);
    if (miny > y) miny = y;
    if (maxy < y) maxy = y;
  }


  if (abs(x1) + abs(x2) > abs(miny) + abs(func(maxy)))
    coef = width/(abs(x1) + abs(x2));
  else
    coef = height/(abs(miny) + abs(maxy));

  if (x1 < 0) xsep = width * abs(x1/(abs(x1) + abs(x2)));
  else if (x2 < 0) xsep = width * abs(x1/(abs(x1) + abs(x2)));
  if (miny < 0) ysep = height * abs(miny/(abs(miny) + abs(maxy)));
  else if (maxy < 0) ysep = height * abs(miny/(abs(miny) + abs(maxy)));

  line(xsep, 0, xsep, height);
  line(0, ysep, width, ysep);

  textFont(f);
  textAlign(LEFT);
  text(int(x1), xsep + int(x1)*coef, ysep-0.2*coef);
  textAlign(CENTER);
  for (int i = int(x1) + 1; i < x2; i++)
  {
     text(i, xsep + i*coef, ysep-0.2*coef);
  }
  textAlign(RIGHT);
  text(int(x2), xsep + int(x2)*coef, ysep-0.2*coef);


  textAlign(LEFT, CENTER);
  text(round(miny), xsep+0.2*coef, ysep - round(miny)*coef);
  text(round(maxy), xsep+0.2*coef, ysep - round(maxy)*coef);

  for (int i = round(miny) + 1; i < round(maxy); i++)
  {
    text(round(i), xsep+0.2*coef, ysep - round(i)*coef);
  }

  do
  {
   y0 = func(x1);
   ly = y0;
   lx = x1;
   x1 += 1/coef;
   y0 = func(x1);
   line(xsep + coef * lx, ysep - coef*ly, xsep + coef*x1, ysep - coef*y0);
  }
  while (x1 <= x2);
}

float func(float x)
{
  return cos(x);
}