def from_str(klass, s):
"""Convert a string representation of a C{RatPoly} to
a C{RatPoly}
@param s:
@type s: string
"""
if s == "nan":
return RatPoly(RatNum(1, 0), 0)
temp_list = []
# Prevent the first negative sign from being seperated.
temp_list += s[0]
i = 0
for sub_str in s[1:]:
if sub_str == "-":
temp_list += "-"
i += 1
elif sub_str == "+":
temp_list.append("")
i += 1
else:
temp_list[i] += sub_str
li = []
for sub_item in temp_list:
li.append([RatTerm.from_str(sub_item).coeff, RatTerm.from_str(sub_item).expt])
poly = RatPoly()
poly.terms = []
degree = max(i[1] for i in li)
i = degree
while i >= 0:
for coeff, expt in li:
if i == expt:
poly.terms += [RatTerm(coeff, expt)]
break
else:
poly.terms += [RatTerm(RatNum(0, 1), i)]
i -= 1
return poly
def assert_eq_str(expected, s):
assert expected == RatTerm.from_str(s)
