positioning pie slice problems - c++

Question

The language I use doesn't have the built ability to create charts of any kind. The following code I found here. It's very old c++ code.
Center of the circle (origin)= (h,k)
Radius = r
...
void Circular_arc(constint h, constint k, constint r, constint start_angle, constint end_angle)
{
int color = getcolor();
float angle = (((start_angle <= end_angle) ? start_angle : end_angle)*(M_PI / 180));
float range = (((end_angle > start_angle) ? end_angle : start_angle)*(M_PI / 180));
float x = (r*cos(angle));
float y = (r*sin(angle));
do
{
putpixel((int)(h + x + 0.5), (int)(k - y + 0.5), color);
angle += 0.001;
x = (r*cos(angle));
y = (r*sin(angle));
} while (angle <= range);
}
...
I converted it to the language I'm using. I've put it in a loop which runs.
The issue with the code is that the slices always start from the same location and draw over what has been previously drawn.
The end result looks like this:
You can see from the differently colored numbers on the screen that there are 3 other arcs being covered up. First the black arc is drawn. Then the red. Then the green. The the yellow one. As the arcs are drawn, they cover up the previously drawn arc. I've inverted the length of the angles to show that there are, in fact 4 total arcs. Again, the black is drawn first, then the red, then the green, then the yellow.
Is there a way to start the next pie slice at the end of the current pie slice?

Answer 1

Because I really don't understand Turbo C++ I can't say for sure. But I think this is your solution:
void Circular_arc(constint h, constint k, constint r, constint start_angle, constint end_angle)
{
static int offset = 0;
start_angle = (start_angle + offset) % 360;
end_angle = (end_angle + offset) % 360;
offset = end_angle;
int color = getcolor();
float angle = (((start_angle <= end_angle) ? start_angle : end_angle)*(M_PI / 180));
float range = (((end_angle > start_angle) ? end_angle : start_angle)*(M_PI / 180));
float x = (r*cos(angle));
float y = (r*sin(angle));
do
{
putpixel((int)(h + x + 0.5), (int)(k - y + 0.5), color);
angle += 0.001;
x = (r*cos(angle));
y = (r*sin(angle));
} while (angle <= range);
}
Let me also say that this is a horrible solution in that it is in no way object oriented. But it seems to be the best you can do without starting over (which you should do.)

Answer 2

I've revamped this and created a method out of it. I did the following to fix my issue. Firstly, I got rid of the process that converted the beginning and ending angles from degree to radians by creating another function that does converts just the ending angle to radians. After Circular_arc is called, I set start_angle equal to the value of end_angle. Less code is written/used. Secondly, I removed the first calculation for finding x,y and moved the second one to the first thing in the loop. This wasn't a necessity, but I'm a big fan of writing as little code as possible. I'm lazy like that. The third biggest part and the whole reason for the OP in the first place was starting the current arc and the end of the previous arc. To do this, I created a variable and set it equal to the value of the start_angle. I then set parameters in the do-while loop to while (start_angle <= (end_angle+angle)). This started the current arc at the end of the previous arc.
The following is my attempt at converting my code to C++. If there are errors then please let me know and I'll do my best fix them. I hope this helps someone in the future!
...
void Circular_arc(constint h, constint k, constint r, constint start_angle, constint end_angle)
{
float angle
angle = start_angle
do
{
x = (r*cos(start_angle));
y = (r*sin(start_angle));
putpixel((int)(h + x + 0.5), (int)(k - y + 0.5), getcolor());
angle += 0.001;
} while (start_angle <= (end_angle+angle));
}
...
Here's what the pie chart looks like so far...