Hi,

I was doing some tests with the jacobian over HyperElliptic Curves,
and I did not quite understand the output of __str__ method of the
elements of such set.

For instance:
field = GF(2**5, 'a')
a = field.gen()
Px = PolynomialRing(field, 'x')
x = Px.gen()

f = x**5 + x**3 + 1
h = x**2 + x

C = HyperellipticCurve(f, h)
J = C.jacobian()

dd = [x * (x + a **30), a * x + 1]
D = J(dd)

sage: D
(x^2 + (a^4 + a)*x, y + a*x + 1)

which is ok, since I asked for the element represented by [x * (x + a
**30), a * x + 1], and

sage:  a**30 == a**4 + a
True

However, using another curve over another field:
Px = PolynomialRing(GF(31), 'x')
x = Px.gen()
f = x**5 + 13*x**4 + 2*x**3 + 4*x**2 + 11*x + 1
C = HyperellipticCurve(f)
J = C.jacobian()
dd = [x**2 + 23 *x +15, 13*x + 28]
D = J(dd)

sage: D
(x^2 + 23*x + 15, y + 18*x + 3)

Which does not seem right, since D was supposed to be represented by
[x**2 + 23 *x +15, 13*x + 28], and

sage: (18 *x + 3) == (13*x + 28)
False

Am I missing something?

Thanks,
- Daniel


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