TCO in Python

TCO (Tail Recursion Optimization) will probably never be supported by CPython because Guido believe TCO will make debugging difficult by messing up tracebacks.

Try the following scripts:

cnt = 1000

def trisum(n, csum): 
  if n == 0: 
    return csum 
  else: 
    return trisum(n-1, csum+n) 
print trisum(cnt,0)

It runs OK when cnt is 10 or 100, but when it's 1000 a runtime error raised: "RuntimeError: maximum recursion depth exceeded".

You can always use iteration to replace recursion like that in the following reference, but that is not FP.

Ref: http://stackoverflow.com/questions/13591970/does-python-optimize-tail-recursion