Is there anyway I could check the number of recursion the program is at. For example, I want to stop the recursion after 2 times. Is there anyway to do that in haskell.
1 Answer
Yes, there is but...
Stopping recursion is normally done when some final state is achieved, something like "I've run out of data to process" or "I have reached the base case." When I see something as arbitrary as "after 2 times" I want to ask where you came up with 2.
However in the interest of answering the question asked:
You need to pass in a counter to the recursive function and bail out when you have done the required number of cycles. For cases like this where the number of cycles is not a matter external to the function, it is typically the case that one creates an auxilary function to introduce it.
myFunction :: Value -> Value
myFunction init = recurse 2 init
where
recurse :: Int -> Value -> Value
recurse 0 result = result
recurse n intermediate = recurse (n-1) (someFun intermediate)
2 Comments
amalloy
The tuple here is a bit odd, rather than simply taking 2 arguments.
John F. Miller
amolloy, yes in looking at it, I think you're right. I had Writer Monad in mind when I was writing this, but decided that was more information than was needed and never took the tuple back out.
for-loopsin haskell - could you explain what you need the recursion for?