hi,

i am trying to write nested for loops to iterate through combinatorial number sequences, nCr. so far, i have gotten 4C2 to work:

1, 2
1, 3
1, 4
2, 3
2, 4
 
however, i am struggling with 4C3.
the loop iterates through:

1, 2, 3
1, 2, 4
1, 3, 4

and then stops and (l) instead of going to:

2, 3, 4

also my control loop doesn't decrease even though i have (i --) as the last condition.

this seems like a terrible way to do this; is there another type of data structure to do this. i would like to have these loops automated to work with whatever combinatorial number sequence it is given. however, i realized that the number of nests has to be equal to n, so that seems it would be difficult to add nests within a loop through iteration.

here's my code so far:
int n = 4;
int digit = 3;
int counter2 = 2;
int counter3 = 3;

void setup()
{
//  combTwo();
    println(combN(4, 3));
}

// my output for the following loop works except for (l). the sequence i get is (jkl) 123, 124, 134, 23.... it never goes back to l, which should be 4. instead j remains iterating between the values of 1 and 2.

void draw()
{
// for(int i = combN(n, digit); i > 0; i --)
// {  println("i" + ", " + i);
     for(int j = 1; j <= n -  2; j ++)
     { println("j" + ", " + j);
       for(int k = counter2; k <= n - 1; k ++)
       { println("k" + ", " + k);
         for(int l = counter3; l < n + 1; l ++)
         {
           println("l" + ", " + l);
//           println(i + ", " + j + ", " + k + ", " + l + ", " + counter3);
         }
         counter3 ++;
       }
       counter2 ++;
     }
// }
}

int factN(int n)
{
  if (n <= 1) return 1;
  else return n * factN(n - 1);
}

int combN(int n, int digit)
{
    if (digit == n) return 1;
    else return factN(n)/(factN(digit) * factN(n - digit));
}

void combTwo()
{
 for(int i = combN(n, digit); i > 0; i --)
 {
     for(int j = 1; j <= n - 1; j ++)
     {
       for(int k = counter2; k < n + 1; k ++)
       {
         println(j + ", " + k);
       }
       counter2 ++;
     }
 }
}

thanks in advance.

cheers,

destro