Problem with dividing

Hi! I am currently making a program that draws a variety of graphs, and I’ve finished with the bar graph and line graph. They work well, and I am trying to add another function: a pie graph.
I am making the drawing part first before I put it together with the entire code, but it does not work well. I think there is a problem with the dividing part. However, I cannot find out the problem. I saved the results as a float variable just in case int can not hold the answer, but it still always ends up with 0. Can someone help me find the problem? The code is below. I boldened the part that causes the problem.

import javax.swing.JOptionPane;
PFont f;

void setup()
  size(2000, 4000);
  arr = new IntList();
  deg = new IntList();
  //title = 
  title = "dss";

int num=0;
String title = "Untitled #1";
IntList arr;
IntList deg;

int a = 0;

void draw()
  int hap = 0;//Is the sum(hap means sum in Korean:))
  for(int i = 0; i < num; i++){
    hap += arr.get(i);
//////////////////////////////////////////////////////////////problem part starts//////////////////////////////////////////////////////////////////////
  float a;
  for(int i = 0; i < num; i++){
    a = arr.get(i) / hap;
    deg.append((int)a * 360);
    println(i+"- a : "+a);
    println(i+" : "+deg.get(i));
//////////////////problem part ends////////////////////////////
  println("hap ="+hap);
  int before = deg.get(0);
  arc(350, 350, 380, 380, radians(0), radians(deg.get(0)));
  for(int i = 1; i < num; i++){
    fill(i*107%255, i*61%255, i*162%255);
    arc(350, 350, 380, 380, radians(before), radians(deg.get(i)));
    before = deg.get(i);
1 Like

if it’s the integer division problem use

a = arr.get(i)/(float)hap; // PCT as 0 .. 1.0

// integer division problem

float f;
int a = 3, b = 2;

f = a/b;

f = a/(float)b;

/* console:


Thank you, but it still doesn’t work…
I think it’s supposed to be the right method of calculating the degrees, isn’t it?

no, rad or deg?

deg = a * 360;
rad =  a * TAU;
1 Like

Umm… I don’t know. Maybe I should try it both.(Although I eventually change into rad later on)
Thank you for your replies!

You have 2 times the variable a. This might cause problems. Once a global int a and then the float a in your method…

What i assume happens :

int a = 0;


float a;
  for(int i = 0; i < num; i++){
    a = arr.get(i) / hap; // float version of a is set. 
    deg.append((int)a * 360);//int version of a (meaning it‘s never set, so only gives 0)
    println(i+"- a : "+a); //these might also be the Int version. 
    println(i+" : "+deg.get(i)); // deg was only set to Int a, which was always 0
1 Like

Oh! Thanks for that, I didn’t realize it. But it doesn’t seem to be the problem…
I am about to get nuts trying to find this thing… Maybe it’s the whole function itself that causes the problem?


(int)a * 360

is not same as

(int)( a * 360 )

esp. if
a = 0 … 1.0

float a = 0.3;
println("(int)a * 360 "+((int)a * 360) );
println("(int)( a * 360 ) "+((int)( a * 360 )) );


(int)a * 360 0
(int)( a * 360 ) 108


Real thanks! I didn’t know that!

sorry, where is a JAVA documentation what talks about that?

  • first ()a
  • second a * b
  • third c + d

anyhow if a program / logic / function not does what you think it should
use heavy diagnostic printing
println("function name : variable "+variable);
a good trick is

boolean diagp = true; // false;


if ( diagp ) println("function name : variable "+variable);

and when testing finished disable all printing

1 Like

Instead of using divide (and hitting divide by zero problem) you could multiply.
So if you wanted to do width/2 you could put width*0.5

Or if you don;t what to work out the percentage. You could try this hack hap = 0.000001


To change Division to multiplication with values that were intended for Division you need to take the inverse, which is a division, and therefore basically comes down to the same.

In your example, you have the Original of :
width/2, where 2 is the factor. To get width/0.5, you need to take the inverse of /2, which is 1/2 = 0.5, so you could just as well use width/2 from the beginning, since it ends up with dividing through the value Anyway.


Oh, Thanks! i didn’t think of that.

Oh, Thanks! That was useful.

1 Like