add read me

venv/lib/python3.12/site-packages/sympy/functions/combinatorial/__init__.py

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+# Stub __init__.py for sympy.functions.combinatorial

venv/lib/python3.12/site-packages/sympy/functions/combinatorial/tests/test_comb_factorials.py

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+from sympy.concrete.products import Product
+from sympy.core.function import expand_func
+from sympy.core.mod import Mod
+from sympy.core.mul import Mul
+from sympy.core import EulerGamma
+from sympy.core.numbers import (Float, I, Rational, nan, oo, pi, zoo)
+from sympy.core.relational import Eq
+from sympy.core.singleton import S
+from sympy.core.symbol import (Dummy, Symbol, symbols)
+from sympy.functions.combinatorial.factorials import (ff, rf, binomial, factorial, factorial2)
+from sympy.functions.elementary.miscellaneous import sqrt
+from sympy.functions.elementary.piecewise import Piecewise
+from sympy.functions.special.gamma_functions import (gamma, polygamma)
+from sympy.polys.polytools import Poly
+from sympy.series.order import O
+from sympy.simplify.simplify import simplify
+from sympy.core.expr import unchanged
+from sympy.core.function import ArgumentIndexError
+from sympy.functions.combinatorial.factorials import subfactorial
+from sympy.functions.special.gamma_functions import uppergamma
+from sympy.testing.pytest import XFAIL, raises, slow
+
+#Solves and Fixes Issue #10388 - This is the updated test for the same solved issue
+
+def test_rf_eval_apply():
+    x, y = symbols('x,y')
+    n, k = symbols('n k', integer=True)
+    m = Symbol('m', integer=True, nonnegative=True)
+
+    assert rf(nan, y) is nan
+    assert rf(x, nan) is nan
+
+    assert unchanged(rf, x, y)
+
+    assert rf(oo, 0) == 1
+    assert rf(-oo, 0) == 1
+
+    assert rf(oo, 6) is oo
+    assert rf(-oo, 7) is -oo
+    assert rf(-oo, 6) is oo
+
+    assert rf(oo, -6) is oo
+    assert rf(-oo, -7) is oo
+
+    assert rf(-1, pi) == 0
+    assert rf(-5, 1 + I) == 0
+
+    assert unchanged(rf, -3, k)
+    assert unchanged(rf, x, Symbol('k', integer=False))
+    assert rf(-3, Symbol('k', integer=False)) == 0
+    assert rf(Symbol('x', negative=True, integer=True), Symbol('k', integer=False)) == 0
+
+    assert rf(x, 0) == 1
+    assert rf(x, 1) == x
+    assert rf(x, 2) == x*(x + 1)
+    assert rf(x, 3) == x*(x + 1)*(x + 2)
+    assert rf(x, 5) == x*(x + 1)*(x + 2)*(x + 3)*(x + 4)
+
+    assert rf(x, -1) == 1/(x - 1)
+    assert rf(x, -2) == 1/((x - 1)*(x - 2))
+    assert rf(x, -3) == 1/((x - 1)*(x - 2)*(x - 3))
+
+    assert rf(1, 100) == factorial(100)
+
+    assert rf(x**2 + 3*x, 2) == (x**2 + 3*x)*(x**2 + 3*x + 1)
+    assert isinstance(rf(x**2 + 3*x, 2), Mul)
+    assert rf(x**3 + x, -2) == 1/((x**3 + x - 1)*(x**3 + x - 2))
+
+    assert rf(Poly(x**2 + 3*x, x), 2) == Poly(x**4 + 8*x**3 + 19*x**2 + 12*x, x)
+    assert isinstance(rf(Poly(x**2 + 3*x, x), 2), Poly)
+    raises(ValueError, lambda: rf(Poly(x**2 + 3*x, x, y), 2))
+    assert rf(Poly(x**3 + x, x), -2) == 1/(x**6 - 9*x**5 + 35*x**4 - 75*x**3 + 94*x**2 - 66*x + 20)
+    raises(ValueError, lambda: rf(Poly(x**3 + x, x, y), -2))
+
+    assert rf(x, m).is_integer is None
+    assert rf(n, k).is_integer is None
+    assert rf(n, m).is_integer is True
+    assert rf(n, k + pi).is_integer is False
+    assert rf(n, m + pi).is_integer is False
+    assert rf(pi, m).is_integer is False
+
+    def check(x, k, o, n):
+        a, b = Dummy(), Dummy()
+        r = lambda x, k: o(a, b).rewrite(n).subs({a:x,b:k})
+        for i in range(-5,5):
+            for j in range(-5,5):
+                assert o(i, j) == r(i, j), (o, n, i, j)
+    check(x, k, rf, ff)
+    check(x, k, rf, binomial)
+    check(n, k, rf, factorial)
+    check(x, y, rf, factorial)
+    check(x, y, rf, binomial)
+
+    assert rf(x, k).rewrite(ff) == ff(x + k - 1, k)
+    assert rf(x, k).rewrite(gamma) == Piecewise(
+        (gamma(k + x)/gamma(x), x > 0),
+        ((-1)**k*gamma(1 - x)/gamma(-k - x + 1), True))
+    assert rf(5, k).rewrite(gamma) == gamma(k + 5)/24
+    assert rf(x, k).rewrite(binomial) == factorial(k)*binomial(x + k - 1, k)
+    assert rf(n, k).rewrite(factorial) == Piecewise(
+        (factorial(k + n - 1)/factorial(n - 1), n > 0),
+        ((-1)**k*factorial(-n)/factorial(-k - n), True))
+    assert rf(5, k).rewrite(factorial) == factorial(k + 4)/24
+    assert rf(x, y).rewrite(factorial) == rf(x, y)
+    assert rf(x, y).rewrite(binomial) == rf(x, y)
+
+    import random
+    from mpmath import rf as mpmath_rf
+    for i in range(100):
+        x = -500 + 500 * random.random()
+        k = -500 + 500 * random.random()
+        assert (abs(mpmath_rf(x, k) - rf(x, k)) < 10**(-15))
+
+
+def test_ff_eval_apply():
+    x, y = symbols('x,y')
+    n, k = symbols('n k', integer=True)
+    m = Symbol('m', integer=True, nonnegative=True)
+
+    assert ff(nan, y) is nan
+    assert ff(x, nan) is nan
+
+    assert unchanged(ff, x, y)
+
+    assert ff(oo, 0) == 1
+    assert ff(-oo, 0) == 1
+
+    assert ff(oo, 6) is oo
+    assert ff(-oo, 7) is -oo
+    assert ff(-oo, 6) is oo
+
+    assert ff(oo, -6) is oo
+    assert ff(-oo, -7) is oo
+
+    assert ff(x, 0) == 1
+    assert ff(x, 1) == x
+    assert ff(x, 2) == x*(x - 1)
+    assert ff(x, 3) == x*(x - 1)*(x - 2)
+    assert ff(x, 5) == x*(x - 1)*(x - 2)*(x - 3)*(x - 4)
+
+    assert ff(x, -1) == 1/(x + 1)
+    assert ff(x, -2) == 1/((x + 1)*(x + 2))
+    assert ff(x, -3) == 1/((x + 1)*(x + 2)*(x + 3))
+
+    assert ff(100, 100) == factorial(100)
+
+    assert ff(2*x**2 - 5*x, 2) == (2*x**2  - 5*x)*(2*x**2 - 5*x - 1)
+    assert isinstance(ff(2*x**2 - 5*x, 2), Mul)
+    assert ff(x**2 + 3*x, -2) == 1/((x**2 + 3*x + 1)*(x**2 + 3*x + 2))
+
+    assert ff(Poly(2*x**2 - 5*x, x), 2) == Poly(4*x**4 - 28*x**3 + 59*x**2 - 35*x, x)
+    assert isinstance(ff(Poly(2*x**2 - 5*x, x), 2), Poly)
+    raises(ValueError, lambda: ff(Poly(2*x**2 - 5*x, x, y), 2))
+    assert ff(Poly(x**2 + 3*x, x), -2) == 1/(x**4 + 12*x**3 + 49*x**2 + 78*x + 40)
+    raises(ValueError, lambda: ff(Poly(x**2 + 3*x, x, y), -2))
+
+
+    assert ff(x, m).is_integer is None
+    assert ff(n, k).is_integer is None
+    assert ff(n, m).is_integer is True
+    assert ff(n, k + pi).is_integer is False
+    assert ff(n, m + pi).is_integer is False
+    assert ff(pi, m).is_integer is False
+
+    assert isinstance(ff(x, x), ff)
+    assert ff(n, n) == factorial(n)
+
+    def check(x, k, o, n):
+        a, b = Dummy(), Dummy()
+        r = lambda x, k: o(a, b).rewrite(n).subs({a:x,b:k})
+        for i in range(-5,5):
+            for j in range(-5,5):
+                assert o(i, j) == r(i, j), (o, n)
+    check(x, k, ff, rf)
+    check(x, k, ff, gamma)
+    check(n, k, ff, factorial)
+    check(x, k, ff, binomial)
+    check(x, y, ff, factorial)
+    check(x, y, ff, binomial)
+
+    assert ff(x, k).rewrite(rf) == rf(x - k + 1, k)
+    assert ff(x, k).rewrite(gamma) == Piecewise(
+        (gamma(x + 1)/gamma(-k + x + 1), x >= 0),
+        ((-1)**k*gamma(k - x)/gamma(-x), True))
+    assert ff(5, k).rewrite(gamma) == 120/gamma(6 - k)
+    assert ff(n, k).rewrite(factorial) == Piecewise(
+        (factorial(n)/factorial(-k + n), n >= 0),
+        ((-1)**k*factorial(k - n - 1)/factorial(-n - 1), True))
+    assert ff(5, k).rewrite(factorial) == 120/factorial(5 - k)
+    assert ff(x, k).rewrite(binomial) == factorial(k) * binomial(x, k)
+    assert ff(x, y).rewrite(factorial) == ff(x, y)
+    assert ff(x, y).rewrite(binomial) == ff(x, y)
+
+    import random
+    from mpmath import ff as mpmath_ff
+    for i in range(100):
+        x = -500 + 500 * random.random()
+        k = -500 + 500 * random.random()
+        a = mpmath_ff(x, k)
+        b = ff(x, k)
+        assert (abs(a - b) < abs(a) * 10**(-15))
+
+
+def test_rf_ff_eval_hiprec():
+    maple = Float('6.9109401292234329956525265438452')
+    us = ff(18, Rational(2, 3)).evalf(32)
+    assert abs(us - maple)/us < 1e-31
+
+    maple = Float('6.8261540131125511557924466355367')
+    us = rf(18, Rational(2, 3)).evalf(32)
+    assert abs(us - maple)/us < 1e-31
+
+    maple = Float('34.007346127440197150854651814225')
+    us = rf(Float('4.4', 32), Float('2.2', 32))
+    assert abs(us - maple)/us < 1e-31
+
+
+def test_rf_lambdify_mpmath():
+    from sympy.utilities.lambdify import lambdify
+    x, y = symbols('x,y')
+    f = lambdify((x,y), rf(x, y), 'mpmath')
+    maple = Float('34.007346127440197')
+    us = f(4.4, 2.2)
+    assert abs(us - maple)/us < 1e-15
+
+
+def test_factorial():
+    x = Symbol('x')
+    n = Symbol('n', integer=True)
+    k = Symbol('k', integer=True, nonnegative=True)
+    r = Symbol('r', integer=False)
+    s = Symbol('s', integer=False, negative=True)
+    t = Symbol('t', nonnegative=True)
+    u = Symbol('u', noninteger=True)
+
+    assert factorial(-2) is zoo
+    assert factorial(0) == 1
+    assert factorial(7) == 5040
+    assert factorial(19) == 121645100408832000
+    assert factorial(31) == 8222838654177922817725562880000000
+    assert factorial(n).func == factorial
+    assert factorial(2*n).func == factorial
+
+    assert factorial(x).is_integer is None
+    assert factorial(n).is_integer is None
+    assert factorial(k).is_integer
+    assert factorial(r).is_integer is None
+
+    assert factorial(n).is_positive is None
+    assert factorial(k).is_positive
+
+    assert factorial(x).is_real is None
+    assert factorial(n).is_real is None
+    assert factorial(k).is_real is True
+    assert factorial(r).is_real is None
+    assert factorial(s).is_real is True
+    assert factorial(t).is_real is True
+    assert factorial(u).is_real is True
+
+    assert factorial(x).is_composite is None
+    assert factorial(n).is_composite is None
+    assert factorial(k).is_composite is None
+    assert factorial(k + 3).is_composite is True
+    assert factorial(r).is_composite is None
+    assert factorial(s).is_composite is None
+    assert factorial(t).is_composite is None
+    assert factorial(u).is_composite is None
+
+    assert factorial(oo) is oo
+
+
+def test_factorial_Mod():
+    pr = Symbol('pr', prime=True)
+    p, q = 10**9 + 9, 10**9 + 33 # prime modulo
+    r, s = 10**7 + 5, 33333333 # composite modulo
+    assert Mod(factorial(pr - 1), pr) == pr - 1
+    assert Mod(factorial(pr - 1), -pr) == -1
+    assert Mod(factorial(r - 1, evaluate=False), r) == 0
+    assert Mod(factorial(s - 1, evaluate=False), s) == 0
+    assert Mod(factorial(p - 1, evaluate=False), p) == p - 1
+    assert Mod(factorial(q - 1, evaluate=False), q) == q - 1
+    assert Mod(factorial(p - 50, evaluate=False), p) == 854928834
+    assert Mod(factorial(q - 1800, evaluate=False), q) == 905504050
+    assert Mod(factorial(153, evaluate=False), r) == Mod(factorial(153), r)
+    assert Mod(factorial(255, evaluate=False), s) == Mod(factorial(255), s)
+    assert Mod(factorial(4, evaluate=False), 3) == S.Zero
+    assert Mod(factorial(5, evaluate=False), 6) == S.Zero
+
+
+def test_factorial_diff():
+    n = Symbol('n', integer=True)
+
+    assert factorial(n).diff(n) == \
+        gamma(1 + n)*polygamma(0, 1 + n)
+    assert factorial(n**2).diff(n) == \
+        2*n*gamma(1 + n**2)*polygamma(0, 1 + n**2)
+    raises(ArgumentIndexError, lambda: factorial(n**2).fdiff(2))
+
+
+def test_factorial_series():
+    n = Symbol('n', integer=True)
+
+    assert factorial(n).series(n, 0, 3) == \
+        1 - n*EulerGamma + n**2*(EulerGamma**2/2 + pi**2/12) + O(n**3)
+
+
+def test_factorial_rewrite():
+    n = Symbol('n', integer=True)
+    k = Symbol('k', integer=True, nonnegative=True)
+
+    assert factorial(n).rewrite(gamma) == gamma(n + 1)
+    _i = Dummy('i')
+    assert factorial(k).rewrite(Product).dummy_eq(Product(_i, (_i, 1, k)))
+    assert factorial(n).rewrite(Product) == factorial(n)
+
+
+def test_factorial2():
+    n = Symbol('n', integer=True)
+
+    assert factorial2(-1) == 1
+    assert factorial2(0) == 1
+    assert factorial2(7) == 105
+    assert factorial2(8) == 384
+
+    # The following is exhaustive
+    tt = Symbol('tt', integer=True, nonnegative=True)
+    tte = Symbol('tte', even=True, nonnegative=True)
+    tpe = Symbol('tpe', even=True, positive=True)
+    tto = Symbol('tto', odd=True, nonnegative=True)
+    tf = Symbol('tf', integer=True, nonnegative=False)
+    tfe = Symbol('tfe', even=True, nonnegative=False)
+    tfo = Symbol('tfo', odd=True, nonnegative=False)
+    ft = Symbol('ft', integer=False, nonnegative=True)
+    ff = Symbol('ff', integer=False, nonnegative=False)
+    fn = Symbol('fn', integer=False)
+    nt = Symbol('nt', nonnegative=True)
+    nf = Symbol('nf', nonnegative=False)
+    nn = Symbol('nn')
+    z = Symbol('z', zero=True)
+    #Solves and Fixes Issue #10388 - This is the updated test for the same solved issue
+    raises(ValueError, lambda: factorial2(oo))
+    raises(ValueError, lambda: factorial2(Rational(5, 2)))
+    raises(ValueError, lambda: factorial2(-4))
+    assert factorial2(n).is_integer is None
+    assert factorial2(tt - 1).is_integer
+    assert factorial2(tte - 1).is_integer
+    assert factorial2(tpe - 3).is_integer
+    assert factorial2(tto - 4).is_integer
+    assert factorial2(tto - 2).is_integer
+    assert factorial2(tf).is_integer is None
+    assert factorial2(tfe).is_integer is None
+    assert factorial2(tfo).is_integer is None
+    assert factorial2(ft).is_integer is None
+    assert factorial2(ff).is_integer is None
+    assert factorial2(fn).is_integer is None
+    assert factorial2(nt).is_integer is None
+    assert factorial2(nf).is_integer is None
+    assert factorial2(nn).is_integer is None
+
+    assert factorial2(n).is_positive is None
+    assert factorial2(tt - 1).is_positive is True
+    assert factorial2(tte - 1).is_positive is True
+    assert factorial2(tpe - 3).is_positive is True
+    assert factorial2(tpe - 1).is_positive is True
+    assert factorial2(tto - 2).is_positive is True
+    assert factorial2(tto - 1).is_positive is True
+    assert factorial2(tf).is_positive is None
+    assert factorial2(tfe).is_positive is None
+    assert factorial2(tfo).is_positive is None
+    assert factorial2(ft).is_positive is None
+    assert factorial2(ff).is_positive is None
+    assert factorial2(fn).is_positive is None
+    assert factorial2(nt).is_positive is None
+    assert factorial2(nf).is_positive is None
+    assert factorial2(nn).is_positive is None
+
+    assert factorial2(tt).is_even is None
+    assert factorial2(tt).is_odd is None
+    assert factorial2(tte).is_even is None
+    assert factorial2(tte).is_odd is None
+    assert factorial2(tte + 2).is_even is True
+    assert factorial2(tpe).is_even is True
+    assert factorial2(tpe).is_odd is False
+    assert factorial2(tto).is_odd is True
+    assert factorial2(tf).is_even is None
+    assert factorial2(tf).is_odd is None
+    assert factorial2(tfe).is_even is None
+    assert factorial2(tfe).is_odd is None
+    assert factorial2(tfo).is_even is False
+    assert factorial2(tfo).is_odd is None
+    assert factorial2(z).is_even is False
+    assert factorial2(z).is_odd is True
+
+
+def test_factorial2_rewrite():
+    n = Symbol('n', integer=True)
+    assert factorial2(n).rewrite(gamma) == \
+        2**(n/2)*Piecewise((1, Eq(Mod(n, 2), 0)), (sqrt(2)/sqrt(pi), Eq(Mod(n, 2), 1)))*gamma(n/2 + 1)
+    assert factorial2(2*n).rewrite(gamma) == 2**n*gamma(n + 1)
+    assert factorial2(2*n + 1).rewrite(gamma) == \
+        sqrt(2)*2**(n + S.Half)*gamma(n + Rational(3, 2))/sqrt(pi)
+
+
+def test_binomial():
+    x = Symbol('x')
+    n = Symbol('n', integer=True)
+    nz = Symbol('nz', integer=True, nonzero=True)
+    k = Symbol('k', integer=True)
+    kp = Symbol('kp', integer=True, positive=True)
+    kn = Symbol('kn', integer=True, negative=True)
+    u = Symbol('u', negative=True)
+    v = Symbol('v', nonnegative=True)
+    p = Symbol('p', positive=True)
+    z = Symbol('z', zero=True)
+    nt = Symbol('nt', integer=False)
+    kt = Symbol('kt', integer=False)
+    a = Symbol('a', integer=True, nonnegative=True)
+    b = Symbol('b', integer=True, nonnegative=True)
+
+    assert binomial(0, 0) == 1
+    assert binomial(1, 1) == 1
+    assert binomial(10, 10) == 1
+    assert binomial(n, z) == 1
+    assert binomial(1, 2) == 0
+    assert binomial(-1, 2) == 1
+    assert binomial(1, -1) == 0
+    assert binomial(-1, 1) == -1
+    assert binomial(-1, -1) == 0
+    assert binomial(S.Half, S.Half) == 1
+    assert binomial(-10, 1) == -10
+    assert binomial(-10, 7) == -11440
+    assert binomial(n, -1) == 0 # holds for all integers (negative, zero, positive)
+    assert binomial(kp, -1) == 0
+    assert binomial(nz, 0) == 1
+    assert expand_func(binomial(n, 1)) == n
+    assert expand_func(binomial(n, 2)) == n*(n - 1)/2
+    assert expand_func(binomial(n, n - 2)) == n*(n - 1)/2
+    assert expand_func(binomial(n, n - 1)) == n
+    assert binomial(n, 3).func == binomial
+    assert binomial(n, 3).expand(func=True) ==  n**3/6 - n**2/2 + n/3
+    assert expand_func(binomial(n, 3)) ==  n*(n - 2)*(n - 1)/6
+    assert binomial(n, n).func == binomial # e.g. (-1, -1) == 0, (2, 2) == 1
+    assert binomial(n, n + 1).func == binomial  # e.g. (-1, 0) == 1
+    assert binomial(kp, kp + 1) == 0
+    assert binomial(kn, kn) == 0 # issue #14529
+    assert binomial(n, u).func == binomial
+    assert binomial(kp, u).func == binomial
+    assert binomial(n, p).func == binomial
+    assert binomial(n, k).func == binomial
+    assert binomial(n, n + p).func == binomial
+    assert binomial(kp, kp + p).func == binomial
+
+    assert expand_func(binomial(n, n - 3)) == n*(n - 2)*(n - 1)/6
+
+    assert binomial(n, k).is_integer
+    assert binomial(nt, k).is_integer is None
+    assert binomial(x, nt).is_integer is False
+
+    assert binomial(gamma(25), 6) == 79232165267303928292058750056084441948572511312165380965440075720159859792344339983120618959044048198214221915637090855535036339620413440000
+    assert binomial(1324, 47) == 906266255662694632984994480774946083064699457235920708992926525848438478406790323869952
+    assert binomial(1735, 43) == 190910140420204130794758005450919715396159959034348676124678207874195064798202216379800
+    assert binomial(2512, 53) == 213894469313832631145798303740098720367984955243020898718979538096223399813295457822575338958939834177325304000
+    assert binomial(3383, 52) == 27922807788818096863529701501764372757272890613101645521813434902890007725667814813832027795881839396839287659777235
+    assert binomial(4321, 51) == 124595639629264868916081001263541480185227731958274383287107643816863897851139048158022599533438936036467601690983780576
+
+    assert binomial(a, b).is_nonnegative is True
+    assert binomial(-1, 2, evaluate=False).is_nonnegative is True
+    assert binomial(10, 5, evaluate=False).is_nonnegative is True
+    assert binomial(10, -3, evaluate=False).is_nonnegative is True
+    assert binomial(-10, -3, evaluate=False).is_nonnegative is True
+    assert binomial(-10, 2, evaluate=False).is_nonnegative is True
+    assert binomial(-10, 1, evaluate=False).is_nonnegative is False
+    assert binomial(-10, 7, evaluate=False).is_nonnegative is False
+
+    # issue #14625
+    for _ in (pi, -pi, nt, v, a):
+        assert binomial(_, _) == 1
+        assert binomial(_, _ - 1) == _
+    assert isinstance(binomial(u, u), binomial)
+    assert isinstance(binomial(u, u - 1), binomial)
+    assert isinstance(binomial(x, x), binomial)
+    assert isinstance(binomial(x, x - 1), binomial)
+
+    #issue #18802
+    assert expand_func(binomial(x + 1, x)) == x + 1
+    assert expand_func(binomial(x, x - 1)) == x
+    assert expand_func(binomial(x + 1, x - 1)) == x*(x + 1)/2
+    assert expand_func(binomial(x**2 + 1, x**2)) == x**2 + 1
+
+    # issue #13980 and #13981
+    assert binomial(-7, -5) == 0
+    assert binomial(-23, -12) == 0
+    assert binomial(Rational(13, 2), -10) == 0
+    assert binomial(-49, -51) == 0
+
+    assert binomial(19, Rational(-7, 2)) == S(-68719476736)/(911337863661225*pi)
+    assert binomial(0, Rational(3, 2)) == S(-2)/(3*pi)
+    assert binomial(-3, Rational(-7, 2)) is zoo
+    assert binomial(kn, kt) is zoo
+
+    assert binomial(nt, kt).func == binomial
+    assert binomial(nt, Rational(15, 6)) == 8*gamma(nt + 1)/(15*sqrt(pi)*gamma(nt - Rational(3, 2)))
+    assert binomial(Rational(20, 3), Rational(-10, 8)) == gamma(Rational(23, 3))/(gamma(Rational(-1, 4))*gamma(Rational(107, 12)))
+    assert binomial(Rational(19, 2), Rational(-7, 2)) == Rational(-1615, 8388608)
+    assert binomial(Rational(-13, 5), Rational(-7, 8)) == gamma(Rational(-8, 5))/(gamma(Rational(-29, 40))*gamma(Rational(1, 8)))
+    assert binomial(Rational(-19, 8), Rational(-13, 5)) == gamma(Rational(-11, 8))/(gamma(Rational(-8, 5))*gamma(Rational(49, 40)))
+
+    # binomial for complexes
+    assert binomial(I, Rational(-89, 8)) == gamma(1 + I)/(gamma(Rational(-81, 8))*gamma(Rational(97, 8) + I))
+    assert binomial(I, 2*I) == gamma(1 + I)/(gamma(1 - I)*gamma(1 + 2*I))
+    assert binomial(-7, I) is zoo
+    assert binomial(Rational(-7, 6), I) == gamma(Rational(-1, 6))/(gamma(Rational(-1, 6) - I)*gamma(1 + I))
+    assert binomial((1+2*I), (1+3*I)) == gamma(2 + 2*I)/(gamma(1 - I)*gamma(2 + 3*I))
+    assert binomial(I, 5) == Rational(1, 3) - I/S(12)
+    assert binomial((2*I + 3), 7) == -13*I/S(63)
+    assert isinstance(binomial(I, n), binomial)
+    assert expand_func(binomial(3, 2, evaluate=False)) == 3
+    assert expand_func(binomial(n, 0, evaluate=False)) == 1
+    assert expand_func(binomial(n, -2, evaluate=False)) == 0
+    assert expand_func(binomial(n, k)) == binomial(n, k)
+
+
+def test_binomial_Mod():
+    p, q = 10**5 + 3, 10**9 + 33 # prime modulo
+    r = 10**7 + 5 # composite modulo
+
+    # A few tests to get coverage
+    # Lucas Theorem
+    assert Mod(binomial(156675, 4433, evaluate=False), p) == Mod(binomial(156675, 4433), p)
+
+    # factorial Mod
+    assert Mod(binomial(1234, 432, evaluate=False), q) == Mod(binomial(1234, 432), q)
+
+    # binomial factorize
+    assert Mod(binomial(253, 113, evaluate=False), r) == Mod(binomial(253, 113), r)
+
+    # using Granville's generalisation of Lucas' Theorem
+    assert Mod(binomial(10**18, 10**12, evaluate=False), p*p) == 3744312326
+
+
+@slow
+def test_binomial_Mod_slow():
+    p, q = 10**5 + 3, 10**9 + 33 # prime modulo
+    r, s = 10**7 + 5, 33333333 # composite modulo
+
+    n, k, m = symbols('n k m')
+    assert (binomial(n, k) % q).subs({n: s, k: p}) == Mod(binomial(s, p), q)
+    assert (binomial(n, k) % m).subs({n: 8, k: 5, m: 13}) == 4
+    assert (binomial(9, k) % 7).subs(k, 2) == 1
+
+    # Lucas Theorem
+    assert Mod(binomial(123456, 43253, evaluate=False), p) == Mod(binomial(123456, 43253), p)
+    assert Mod(binomial(-178911, 237, evaluate=False), p) == Mod(-binomial(178911 + 237 - 1, 237), p)
+    assert Mod(binomial(-178911, 238, evaluate=False), p) == Mod(binomial(178911 + 238 - 1, 238), p)
+
+    # factorial Mod
+    assert Mod(binomial(9734, 451, evaluate=False), q) == Mod(binomial(9734, 451), q)
+    assert Mod(binomial(-10733, 4459, evaluate=False), q) == Mod(binomial(-10733, 4459), q)
+    assert Mod(binomial(-15733, 4458, evaluate=False), q) == Mod(binomial(-15733, 4458), q)
+    assert Mod(binomial(23, -38, evaluate=False), q) is S.Zero
+    assert Mod(binomial(23, 38, evaluate=False), q) is S.Zero
+
+    # binomial factorize
+    assert Mod(binomial(753, 119, evaluate=False), r) == Mod(binomial(753, 119), r)
+    assert Mod(binomial(3781, 948, evaluate=False), s) == Mod(binomial(3781, 948), s)
+    assert Mod(binomial(25773, 1793, evaluate=False), s) == Mod(binomial(25773, 1793), s)
+    assert Mod(binomial(-753, 118, evaluate=False), r) == Mod(binomial(-753, 118), r)
+    assert Mod(binomial(-25773, 1793, evaluate=False), s) == Mod(binomial(-25773, 1793), s)
+
+
+def test_binomial_diff():
+    n = Symbol('n', integer=True)
+    k = Symbol('k', integer=True)
+
+    assert binomial(n, k).diff(n) == \
+        (-polygamma(0, 1 + n - k) + polygamma(0, 1 + n))*binomial(n, k)
+    assert binomial(n**2, k**3).diff(n) == \
+        2*n*(-polygamma(
+            0, 1 + n**2 - k**3) + polygamma(0, 1 + n**2))*binomial(n**2, k**3)
+
+    assert binomial(n, k).diff(k) == \
+        (-polygamma(0, 1 + k) + polygamma(0, 1 + n - k))*binomial(n, k)
+    assert binomial(n**2, k**3).diff(k) == \
+        3*k**2*(-polygamma(
+            0, 1 + k**3) + polygamma(0, 1 + n**2 - k**3))*binomial(n**2, k**3)
+    raises(ArgumentIndexError, lambda: binomial(n, k).fdiff(3))
+
+
+def test_binomial_rewrite():
+    n = Symbol('n', integer=True)
+    k = Symbol('k', integer=True)
+    x = Symbol('x')
+
+    assert binomial(n, k).rewrite(
+        factorial) == factorial(n)/(factorial(k)*factorial(n - k))
+    assert binomial(
+        n, k).rewrite(gamma) == gamma(n + 1)/(gamma(k + 1)*gamma(n - k + 1))
+    assert binomial(n, k).rewrite(ff) == ff(n, k) / factorial(k)
+    assert binomial(n, x).rewrite(ff) == binomial(n, x)
+
+
+@XFAIL
+def test_factorial_simplify_fail():
+    # simplify(factorial(x + 1).diff(x) - ((x + 1)*factorial(x)).diff(x))) == 0
+    from sympy.abc import x
+    assert simplify(x*polygamma(0, x + 1) - x*polygamma(0, x + 2) +
+                    polygamma(0, x + 1) - polygamma(0, x + 2) + 1) == 0
+
+
+def test_subfactorial():
+    assert all(subfactorial(i) == ans for i, ans in enumerate(
+        [1, 0, 1, 2, 9, 44, 265, 1854, 14833, 133496]))
+    assert subfactorial(oo) is oo
+    assert subfactorial(nan) is nan
+    assert subfactorial(23) == 9510425471055777937262
+    assert unchanged(subfactorial, 2.2)
+
+    x = Symbol('x')
+    assert subfactorial(x).rewrite(uppergamma) == uppergamma(x + 1, -1)/S.Exp1
+
+    tt = Symbol('tt', integer=True, nonnegative=True)
+    tf = Symbol('tf', integer=True, nonnegative=False)
+    tn = Symbol('tf', integer=True)
+    ft = Symbol('ft', integer=False, nonnegative=True)
+    ff = Symbol('ff', integer=False, nonnegative=False)
+    fn = Symbol('ff', integer=False)
+    nt = Symbol('nt', nonnegative=True)
+    nf = Symbol('nf', nonnegative=False)
+    nn = Symbol('nf')
+    te = Symbol('te', even=True, nonnegative=True)
+    to = Symbol('to', odd=True, nonnegative=True)
+    assert subfactorial(tt).is_integer
+    assert subfactorial(tf).is_integer is None
+    assert subfactorial(tn).is_integer is None
+    assert subfactorial(ft).is_integer is None
+    assert subfactorial(ff).is_integer is None
+    assert subfactorial(fn).is_integer is None
+    assert subfactorial(nt).is_integer is None
+    assert subfactorial(nf).is_integer is None
+    assert subfactorial(nn).is_integer is None
+    assert subfactorial(tt).is_nonnegative
+    assert subfactorial(tf).is_nonnegative is None
+    assert subfactorial(tn).is_nonnegative is None
+    assert subfactorial(ft).is_nonnegative is None
+    assert subfactorial(ff).is_nonnegative is None
+    assert subfactorial(fn).is_nonnegative is None
+    assert subfactorial(nt).is_nonnegative is None
+    assert subfactorial(nf).is_nonnegative is None
+    assert subfactorial(nn).is_nonnegative is None
+    assert subfactorial(tt).is_even is None
+    assert subfactorial(tt).is_odd is None
+    assert subfactorial(te).is_odd is True
+    assert subfactorial(to).is_even is True