def test_Sum_doit():
f = Function('f')
assert Sum(n * Integral(a**2), (n, 0, 2)).doit() == a**3
assert Sum(n*Integral(a**2), (n, 0, 2)).doit(deep=False) == \
3*Integral(a**2)
assert summation(n * Integral(a**2), (n, 0, 2)) == 3 * Integral(a**2)
# test nested sum evaluation
s = Sum(Sum(Sum(2, (z, 1, n + 1)), (y, x + 1, n)), (x, 1, n))
assert 0 == (s.doit() - n * (n + 1) * (n - 1)).factor()
assert Sum(Sum(KroneckerDelta(m, n), (m, 1, 3)), (n, 1, 3)).doit() == 3
assert Sum(Sum(KroneckerDelta(k, m), (m, 1, 3)), (n, 1, 3)).doit() == \
3*Piecewise((1, And(Integer(1) <= k, k <= 3)), (0, True))
assert Sum(f(n)*Sum(KroneckerDelta(m, n), (m, 0, oo)), (n, 1, 3)).doit() == \
f(1) + f(2) + f(3)
assert Sum(f(n)*Sum(KroneckerDelta(m, n), (m, 0, oo)), (n, 1, oo)).doit() == \
Sum(Piecewise((f(n), And(Le(0, n), n < oo)), (0, True)), (n, 1, oo))
l = Symbol('l', integer=True, positive=True)
assert Sum(f(l)*Sum(KroneckerDelta(m, l), (m, 0, oo)), (l, 1, oo)).doit() == \
Sum(f(l), (l, 1, oo))
# issue sympy/sympy#2597
nmax = symbols('N', integer=True, positive=True)
pw = Piecewise((1, And(Integer(1) <= n, n <= nmax)), (0, True))
assert Sum(pw, (n, 1, nmax)).doit() == Sum(pw, (n, 1, nmax))
def pdf(self, x):
x = sympify(x)
if x.is_number:
if x.is_Integer and x >= 1 and x <= self.sides:
return Rational(1, self.sides)
return S.Zero
if x.is_Symbol:
i = Dummy('i', integer=True, positive=True)
return Sum(KroneckerDelta(x, i) / self.sides, (i, 1, self.sides))
raise ValueError(
"'x' expected as an argument of type 'number' or 'symbol', "
"not %s" % (type(x)))
def test_kronecker_delta():
i, j = symbols('i j')
k = Symbol('k', nonzero=True)
assert KroneckerDelta(1, 1) == 1
assert KroneckerDelta(1, 2) == 0
assert KroneckerDelta(k, 0) == 0
assert KroneckerDelta(x, x) == 1
assert KroneckerDelta(x**2 - y**2, x**2 - y**2) == 1
assert KroneckerDelta(i, i) == 1
assert KroneckerDelta(i, i + 1) == 0
assert KroneckerDelta(0, 0) == 1
assert KroneckerDelta(0, 1) == 0
assert KroneckerDelta(i + k, i) == 0
assert KroneckerDelta(i + k, i + k) == 1
assert KroneckerDelta(i + k, i + 1 + k) == 0
assert KroneckerDelta(i, j).subs({i: 1, j: 0}) == 0
assert KroneckerDelta(i, j).subs({i: 3, j: 3}) == 1
assert KroneckerDelta(i, j)**0 == 1
for n in range(1, 10):
assert KroneckerDelta(i, j)**n == KroneckerDelta(i, j)
assert KroneckerDelta(i, j)**-n == 1 / KroneckerDelta(i, j)
assert KroneckerDelta(i, j).is_integer is True
assert adjoint(KroneckerDelta(i, j)) == KroneckerDelta(i, j)
assert conjugate(KroneckerDelta(i, j)) == KroneckerDelta(i, j)
assert transpose(KroneckerDelta(i, j)) == KroneckerDelta(i, j)
# to test if canonical
assert KroneckerDelta(i, j) == KroneckerDelta(j, i)