ouch! you just hit on one of my pet peeves... bad spelling.

It's "occurrence", not "occurance". Your code may be the greatest thing in the world since sliced bread, but if routine names contain spelling mistakes people are going to believe that the code contains other shoddinesses, thus you wind up needlessly damaging your reputation.

Worse, client programmers using your code are going to stumble and trip, because they're going to try and call count_occurrences and fail miserably.