How to handle maximum recursion depth?

Question

Many languages (such as python) have a set maximum recursion depth. I realize you can change that depth, or simply not write recursive functions altogether, but if you do write a recursive function and you hit that maximum recursion depth, how would you prepare for and handle that?

Answer 1

The only thing you really can do at that point is to let the user know that something has gone wrong and the task cannot be performed as designed.

Answer 2

Have a parameter in the function signature that gets incremented for each call. When it gets near the maximum recursion depth, do something before it is reached.

Here is a ruby-ish pseudo code example:

def my_recursive_function(current_depth)
   # do stuff
   if current_depth >= MAX_RECURSION_LIMIT
     # throw exception, or output helpful information or return default value
   else
     my_recursive_function(current_depth+1)
   end

end

Answer 3

I think the best way is to avoid writing recursive code that has any chance of reaching the maximum depth. There's always a way to re-write a recursive algorithm as an iterative one, so just do that.

If you're dead set on writing recursive code that may hit the limit, then write a backup iterative version, catch the recursion exceeded exception and switch to the iterative one.