vectorCounter

I don't know how many times I needed to rewrite this function. Its such a simple thing, hardly worth sharing, but now I won't have to rewrite it anymore.

I needed to iterate over a length-N vector from a start vector to a finish vector and at each iteration, check some conditions.

For example, a two-counter base 3 example would be
0 0
0 1
0 2
1 0
1 1
....etc...
2 1
2 2 <== Done

Here is the output from the demo mode of vectorCounter:

east significant count component is to the left
-----------------------------------------
start condition: -3 2 -1
end condition: 2 3 1
hit conditions: 2 3 5 7 10 12 30 33
pseudo code:
do:
[newVec, newCount, doneFlag, hitIndex] = vectorCounter(xEnd, xStart, hitList, oldVec, oldCount)
oldVec = newVec
oldCount = newCount

do something here ....

until(doneFlag == true)

-----------------------------------------
old count----old vector count-------hit index
1 [ -3, 2, -1]
2 [ -2, 2, -1] 1
3 [ -1, 2, -1] 2
4 [ 0, 2, -1]
5 [ 1, 2, -1] 3
6 [ 2, 2, -1]
7 [ -3, 3, -1] 4
8 [ -2, 3, -1]
9 [ -1, 3, -1]
10 [ 0, 3, -1] 5
11 [ 1, 3, -1]
12 [ 2, 3, -1] 6
13 [ -3, 2, 0]
14 [ -2, 2, 0]
15 [ -1, 2, 0]
16 [ 0, 2, 0]
17 [ 1, 2, 0]
18 [ 2, 2, 0]
19 [ -3, 3, 0]
20 [ -2, 3, 0]
21 [ -1, 3, 0]
22 [ 0, 3, 0]
23 [ 1, 3, 0]
24 [ 2, 3, 0]
25 [ -3, 2, 1]
26 [ -2, 2, 1]
27 [ -1, 2, 1]
28 [ 0, 2, 1]
29 [ 1, 2, 1]
30 [ 2, 2, 1] 7
31 [ -3, 3, 1]
32 [ -2, 3, 1]
33 [ -1, 3, 1] 8
34 [ 0, 3, 1]
35 [ 1, 3, 1]
36 [ 2, 3, 1] 0 <== DONE

Limitations: the iterators must step by 1 for each counter:
-3->-2->-1 is OK
-3->-1->-2 is NOT OK

As I noted, it is such a simple thing, it is hardly worth sharing. But...

michaelB brost Feb 2009