def flatten_result(source):
"""
Turns the given source sequence into a list of reg-exp possibilities and
their arguments. Returns a list of strings and a list of argument lists.
Each of the two lists will be of the same length.
"""
if source is None:
return [''], [[]]
if isinstance(source, Group):
if source[1] is None:
params = []
else:
params = [source[1]]
return [source[0]], [params]
result = ['']
result_args = [[]]
pos = last = 0
for pos, elt in enumerate(source):
if isinstance(elt, six.string_types):
continue
piece = ''.join(source[last:pos])
if isinstance(elt, Group):
piece += elt[0]
param = elt[1]
else:
param = None
last = pos + 1
for i in range(len(result)):
result[i] += piece
if param:
result_args[i].append(param)
if isinstance(elt, (Choice, NonCapture)):
if isinstance(elt, NonCapture):
elt = [elt]
inner_result, inner_args = [], []
for item in elt:
res, args = flatten_result(item)
inner_result.extend(res)
inner_args.extend(args)
new_result = []
new_args = []
for item, args in zip(result, result_args):
for i_item, i_args in zip(inner_result, inner_args):
new_result.append(item + i_item)
new_args.append(args[:] + i_args)
result = new_result
result_args = new_args
if pos >= last:
piece = ''.join(source[last:])
for i in range(len(result)):
result[i] += piece
return result, result_args
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