Recently I was translating a piece of C++ code to Java.
I'm wondering how others might make this translation.
Thanks, JSH.
double d2;
double d3;
double e;
C++ test:
int test = (int(d2 > e) << 1) + int(d3 > e);
Java test:
int t = d2 > e ? 1<<1 : 0;
int test = d3 > e ? t+1 : t;
switch(test)
{ case(0):
case(1):
case(2):
case(3):
}
Thanks for the responses.
Yes, the nested if/else seems more clear in the above short example.
Now I wonder about the original author's motivation for
the use of switch statement. Code clarity, optimization, idiomatics?
Somehow the code seems easier for me to read with the use of the
switch simply because of the length of the intervening code.
void curve4_div::recursive_bezier(double x1, double y1, double x2,
double y2, double x3, double y3, double x4, double y4, unsigned level) {
if (level > curve_recursion_limit) {
return;
}
// Calculate all the mid-points of the line segments
//----------------------
double x12 = (x1 + x2) / 2;
double y12 = (y1 + y2) / 2;
double x23 = (x2 + x3) / 2;
double y23 = (y2 + y3) / 2;
double x34 = (x3 + x4) / 2;
double y34 = (y3 + y4) / 2;
double x123 = (x12 + x23) / 2;
double y123 = (y12 + y23) / 2;
double x234 = (x23 + x34) / 2;
double y234 = (y23 + y34) / 2;
double x1234 = (x123 + x234) / 2;
double y1234 = (y123 + y234) / 2;
// Try to approximate the full cubic curve by a single straight line
//------------------
double dx = x4 - x1;
double dy = y4 - y1;
double d2 = fabs(((x2 - x4) * dy - (y2 - y4) * dx));
double d3 = fabs(((x3 - x4) * dy - (y3 - y4) * dx));
double da1, da2, k;
switch ((int(d2 > curve_collinearity_epsilon) << 1) +
int(d3 > curve_collinearity_epsilon)) {
case 0:
// All collinear OR p1==p4
//----------------------
k = dx * dx + dy * dy;
if (k == 0) {
d2 = calc_sq_distance(x1, y1, x2, y2);
d3 = calc_sq_distance(x4, y4, x3, y3);
} else {
k = 1 / k;
da1 = x2 - x1;
da2 = y2 - y1;
d2 = k * (da1 * dx + da2 * dy);
da1 = x3 - x1;
da2 = y3 - y1;
d3 = k * (da1 * dx + da2 * dy);
if (d2 > 0 && d2 < 1 && d3 > 0 && d3 < 1) {
// Simple collinear case, 1---2---3---4
// We can leave just two endpoints
return;
}
if (d2 <= 0)
d2 = calc_sq_distance(x2, y2, x1, y1);
else if (d2 >= 1)
d2 = calc_sq_distance(x2, y2, x4, y4);
else
d2 = calc_sq_distance(x2, y2, x1 + d2 * dx, y1 + d2 * dy);
if (d3 <= 0)
d3 = calc_sq_distance(x3, y3, x1, y1);
else if (d3 >= 1)
d3 = calc_sq_distance(x3, y3, x4, y4);
else
d3 = calc_sq_distance(x3, y3, x1 + d3 * dx, y1 + d3 * dy);
}
if (d2 > d3) {
if (d2 < m_distance_tolerance_square) {
m_points.add(point_d(x2, y2));
return;
}
} else {
if (d3 < m_distance_tolerance_square) {
m_points.add(point_d(x3, y3));
return;
}
}
break;
case 1:
// p1,p2,p4 are collinear, p3 is significant
//----------------------
if (d3 * d3 <= m_distance_tolerance_square * (dx * dx + dy * dy)) {
if (m_angle_tolerance < curve_angle_tolerance_epsilon) {
m_points.add(point_d(x23, y23));
return;
}
// Angle Condition
//----------------------
da1 = fabs(atan2(y4 - y3, x4 - x3) - atan2(y3 - y2, x3 - x2));
if (da1 >= pi)
da1 = 2 * pi - da1;
if (da1 < m_angle_tolerance) {
m_points.add(point_d(x2, y2));
m_points.add(point_d(x3, y3));
return;
}
if (m_cusp_limit != 0.0) {
if (da1 > m_cusp_limit) {
m_points.add(point_d(x3, y3));
return;
}
}
}
break;
case 2:
// p1,p3,p4 are collinear, p2 is significant
//----------------------
if (d2 * d2 <= m_distance_tolerance_square * (dx * dx + dy * dy)) {
if (m_angle_tolerance < curve_angle_tolerance_epsilon) {
m_points.add(point_d(x23, y23));
return;
}
// Angle Condition
//----------------------
da1 = fabs(atan2(y3 - y2, x3 - x2) - atan2(y2 - y1, x2 - x1));
if (da1 >= pi)
da1 = 2 * pi - da1;
if (da1 < m_angle_tolerance) {
m_points.add(point_d(x2, y2));
m_points.add(point_d(x3, y3));
return;
}
if (m_cusp_limit != 0.0) {
if (da1 > m_cusp_limit) {
m_points.add(point_d(x2, y2));
return;
}
}
}
break;
case 3:
// Regular case
//-----------------
if ((d2 + d3) * (d2 + d3) <= m_distance_tolerance_square * (dx * dx
+ dy * dy)) {
// If the curvature doesn't exceed the distance_tolerance value
// we tend to finish subdivisions.
//----------------------
if (m_angle_tolerance < curve_angle_tolerance_epsilon) {
m_points.add(point_d(x23, y23));
return;
}
// Angle & Cusp Condition
//----------------------
k = atan2(y3 - y2, x3 - x2);
da1 = fabs(k - atan2(y2 - y1, x2 - x1));
da2 = fabs(atan2(y4 - y3, x4 - x3) - k);
if (da1 >= pi)
da1 = 2 * pi - da1;
if (da2 >= pi)
da2 = 2 * pi - da2;
if (da1 + da2 < m_angle_tolerance) {
// Finally we can stop the recursion
//----------------------
m_points.add(point_d(x23, y23));
return;
}
if (m_cusp_limit != 0.0) {
if (da1 > m_cusp_limit) {
m_points.add(point_d(x2, y2));
return;
}
if (da2 > m_cusp_limit) {
m_points.add(point_d(x3, y3));
return;
}
}
}
break;
}
// Continue subdivision
//----------------------
recursive_bezier(x1, y1, x12, y12, x123, y123, x1234, y1234, level + 1);
recursive_bezier(x1234, y1234, x234, y234, x34, y34, x4, y4, level + 1);
}
