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def tokenize(s, sep="()", ws=" \t\n"):
L = []
food = 0
for i, c in enumerate(s):
if c in sep or c in ws:
if food > 0:
L.append(s[i-food:i])
if c in sep:
L.append(c)
food = 0
elif i+1 == len(s):
L.append(s[i-food:])
else:
food += 1
return L
def _parse_tokens(tokens, depth=0):
L = []
i = 0
while i < len(tokens):
el = tokens[i]
if el == '(':
expr, skip = _parse_tokens(tokens[i+1:], depth+1)
L.append(expr)
i += skip + 1
elif el == ')':
assert depth > 0, "Missing open bracket..."
return L, i+1
else:
L.append(el)
i += 1
assert depth == 0, "Missing close bracket..."
return L, i
def parse(s):
tokens = tokenize(s)
expr, size = _parse_tokens(tokens)
return expr[0]
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