On Fri, Dec 31, 2021 at 2:00 AM hongy...@gmail.com <hongyi.z...@gmail.com> wrote: > > I try to compute the factorial of a large number with tail-recursion > optimization decorator in Python3. The following code snippet is converted > from the code snippet given here [1] by the following steps: > > $ pyenv shell datasci > $ python --version > Python 3.9.1 > $ pip install 2to3 > $ 2to3 -w this-script.py > > ``` > # This program shows off a python decorator( > # which implements tail call optimization. It > # does this by throwing an exception if it is > # its own grandparent, and catching such > # exceptions to recall the stack. > > import sys > > class TailRecurseException: > def __init__(self, args, kwargs): > self.args = args > self.kwargs = kwargs >
If it's an exception, it needs to subclass Exception or BaseException. (Also, is this REALLY an optimization? Exception handling isn't the fastest. Yes, it avoids some measure of recursion depth, but it looks like a pretty inefficient way to do things. Python is not Lisp, and there are very very few algorithms that actually benefit from tail call optimization that wouldn't benefit far more from other ways of doing the same thing.) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
