Duncan Booth wrote:
> My other problem with this is that the decorator is very fragile although
> this may be fixable
This version should be more robust against exceptions:
class tail_recursive(object):
"""
tail_recursive decorator based on Kay Schluehr's recipe
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/496691
"""
CONTINUE = object() # sentinel
def __init__(self, func):
self.func = func
self.firstcall = True
def __call__(self, *args, **kwd):
try:
if self.firstcall: # start looping
self.firstcall = False
while True:
result = self.func(*args, **kwd)
if result is self.CONTINUE: # update arguments
args, kwd = self.argskwd
else: # last call
break
else: # return the arguments of the tail call
self.argskwd = args, kwd
return self.CONTINUE
except: # reset and re-raise
self.firstcall = True
raise
else: # reset and exit
self.firstcall = True
return result
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