def tailcall(f):
'''Decorator that implements tail call optimization.
Supports cooperative tail call - even when only one of the functions
is
decorated, and all exceptions pass through it. You can tell the
functions
that have been tail optimized because they have "tco" before them in
the
stack frame.
The only caveat is that if you attempt to decorate a function that
isn't
called in a tail recursive fashion from another decorated function,
you'll
get wrong results.'''
tdata = [False] #[Optimizing?]
DO_CALL = object() #Call marker
def tco(*a, **aa):
if tdata[0]:
return DO_CALL, a, aa
else:
tdata[0] = True
ret = f(*a, **aa)
while type(ret) is tuple and ret and ret[0] is DO_CALL:
ret = f(*ret[1], **ret[2])
tdata[0] = False
return ret
tco.__doc__ = f.__doc__
return tco