def test_postorder_traversal():
expr = z + w * (x + y)
expected = [z, w, x, y, x + y, w * (x + y), w * (x + y) + z]
assert list(postorder_traversal(expr, keys=default_sort_key)) == expected
assert list(postorder_traversal(expr, keys=True)) == expected
expr = Piecewise((x, x < 1), (x**2, True))
expected = [
x, 1, x, x < 1,
ExprCondPair(x, x < 1), true, 2, x, x**2,
ExprCondPair(x**2, True),
Piecewise((x, x < 1), (x**2, True))
]
assert list(postorder_traversal(expr, keys=default_sort_key)) == expected
assert list(postorder_traversal(
[expr], keys=default_sort_key)) == expected + [[expr]]
assert list(
postorder_traversal(Integral(x**2, (x, 0, 1)),
keys=default_sort_key)) == [
2, x, x**2, 0, 1, x,
Tuple(x, 0, 1),
Integral(x**2, Tuple(x, 0, 1))
]
assert list(postorder_traversal(
('abc',
('d',
'ef')))) == ['abc', 'd', 'ef', ('d', 'ef'), ('abc', ('d', 'ef'))]
def eval_sum_hyper(f, i_a_b):
from diofant.logic.boolalg import And
i, a, b = i_a_b
if (b - a).is_Integer:
# We are never going to do better than doing the sum in the obvious way
return
old_sum = Sum(f, (i, a, b))
if b != S.Infinity:
if a == S.NegativeInfinity:
res = _eval_sum_hyper(f.subs(i, -i), i, -b)
if res is not None:
return Piecewise(res, (old_sum, True))
else:
res1 = _eval_sum_hyper(f, i, a)
res2 = _eval_sum_hyper(f, i, b + 1)
if res1 is None or res2 is None:
return
(res1, cond1), (res2, cond2) = res1, res2
cond = And(cond1, cond2)
if cond == S.false:
return
return Piecewise((res1 - res2, cond), (old_sum, True))
if a == S.NegativeInfinity:
res1 = _eval_sum_hyper(f.subs(i, -i), i, 1)
res2 = _eval_sum_hyper(f, i, 0)
if res1 is None or res2 is None:
return
res1, cond1 = res1
res2, cond2 = res2
cond = And(cond1, cond2)
if cond == S.false:
return
return Piecewise((res1 + res2, cond), (old_sum, True))
# Now b == oo, a != -oo
res = _eval_sum_hyper(f, i, a)
if res is not None:
r, c = res
if c == S.false:
if r.is_number:
f = f.subs(i, Dummy('i', integer=True, positive=True) + a)
if f.is_positive or f.is_zero:
return S.Infinity
elif f.is_negative:
return S.NegativeInfinity
return
return Piecewise(res, (old_sum, True))
def _print_Assignment(self, expr):
from diofant.functions.elementary.piecewise import Piecewise
from diofant.matrices.expressions.matexpr import MatrixSymbol
from diofant.tensor.indexed import IndexedBase
lhs = expr.lhs
rhs = expr.rhs
# We special case assignments that take multiple lines
if isinstance(expr.rhs, Piecewise):
# Here we modify Piecewise so each expression is now
# an Assignment, and then continue on the print.
expressions = []
conditions = []
for (e, c) in rhs.args:
expressions.append(Assignment(lhs, e))
conditions.append(c)
temp = Piecewise(*zip(expressions, conditions))
return self._print(temp)
elif isinstance(lhs, MatrixSymbol):
# Here we form an Assignment for each element in the array,
# printing each one.
lines = []
for (i, j) in self._traverse_matrix_indices(lhs):
temp = Assignment(lhs[i, j], rhs[i, j])
code0 = self._print(temp)
lines.append(code0)
return "\n".join(lines)
elif self._settings["contract"] and (lhs.has(IndexedBase) or
rhs.has(IndexedBase)):
# Here we check if there is looping to be done, and if so
# print the required loops.
return self._doprint_loops(rhs, lhs)
else:
lhs_code = self._print(lhs)
rhs_code = self._print(rhs)
return self._get_statement("%s = %s" % (lhs_code, rhs_code))
def __new__(cls, p1, pt=None, angle=None, **kwargs):
p1 = Point(p1)
if pt is not None and angle is None:
try:
p2 = Point(pt)
except NotImplementedError:
from diofant.utilities.misc import filldedent
raise ValueError(filldedent('''
The 2nd argument was not a valid Point; if
it was meant to be an angle it should be
given with keyword "angle".'''))
if p1 == p2:
raise ValueError('A Ray requires two distinct points.')
elif angle is not None and pt is None:
# we need to know if the angle is an odd multiple of pi/2
c = pi_coeff(sympify(angle))
p2 = None
if c is not None:
if c.is_Rational:
if c.q == 2:
if c.p == 1:
p2 = p1 + Point(0, 1)
elif c.p == 3:
p2 = p1 + Point(0, -1)
elif c.q == 1:
if c.p == 0:
p2 = p1 + Point(1, 0)
elif c.p == 1:
p2 = p1 + Point(-1, 0)
if p2 is None:
c *= S.Pi
else:
c = angle % (2*S.Pi)
if not p2:
m = 2*c/S.Pi
left = And(1 < m, m < 3) # is it in quadrant 2 or 3?
x = Piecewise((-1, left), (Piecewise((0, Eq(m % 1, 0)), (1, True)), True))
y = Piecewise((-tan(c), left), (Piecewise((1, Eq(m, 1)), (-1, Eq(m, 3)), (tan(c), True)), True))
p2 = p1 + Point(x, y)
else:
raise ValueError('A 2nd point or keyword "angle" must be used.')
return LinearEntity.__new__(cls, p1, p2, **kwargs)
def _eval_rewrite_as_Piecewise(self, arg):
if arg.is_extended_real:
return Piecewise((1, arg > 0), (Rational(1, 2), Eq(arg, 0)),
(0, True))
def eval_sum_symbolic(f, limits):
from diofant.functions import harmonic, bernoulli
f_orig = f
(i, a, b) = limits
if not f.has(i):
return f * (b - a + 1)
# Linearity
if f.is_Mul:
L, R = f.as_two_terms()
if not L.has(i):
sR = eval_sum_symbolic(R, (i, a, b))
if sR:
return L * sR
if not R.has(i):
sL = eval_sum_symbolic(L, (i, a, b))
if sL:
return R * sL
try:
f = apart(f, i) # see if it becomes an Add
except PolynomialError:
pass
if f.is_Add:
L, R = f.as_two_terms()
lrsum = telescopic(L, R, (i, a, b))
if lrsum:
return lrsum
lsum = eval_sum_symbolic(L, (i, a, b))
rsum = eval_sum_symbolic(R, (i, a, b))
if None not in (lsum, rsum):
r = lsum + rsum
if r is not S.NaN:
return r
# Polynomial terms with Faulhaber's formula
n = Wild('n')
result = f.match(i**n)
if result is not None:
n = result[n]
if n.is_Integer:
if n >= 0:
if (b is S.Infinity and a is not S.NegativeInfinity) or \
(a is S.NegativeInfinity and b is not S.Infinity):
return S.Infinity
return ((bernoulli(n + 1, b + 1) - bernoulli(n + 1, a)) /
(n + 1)).expand()
elif a.is_Integer and a >= 1:
if n == -1:
return harmonic(b) - harmonic(a - 1)
else:
return harmonic(b, abs(n)) - harmonic(a - 1, abs(n))
if not (a.has(S.Infinity, S.NegativeInfinity)
or b.has(S.Infinity, S.NegativeInfinity)):
# Geometric terms
c1 = Wild('c1', exclude=[i])
c2 = Wild('c2', exclude=[i])
c3 = Wild('c3', exclude=[i])
e = f.match(c1**(c2 * i + c3))
if e is not None:
p = (c1**c3).subs(e)
q = (c1**c2).subs(e)
r = p * (q**a - q**(b + 1)) / (1 - q)
l = p * (b - a + 1)
return Piecewise((l, Eq(q, S.One)), (r, True))
r = gosper_sum(f, (i, a, b))
if r is not None and r.is_finite:
return r
return eval_sum_hyper(f_orig, (i, a, b))
def heurisch_wrapper(f,
x,
rewrite=False,
hints=None,
mappings=None,
retries=3,
degree_offset=0,
unnecessary_permutations=None):
"""
A wrapper around the heurisch integration algorithm.
This method takes the result from heurisch and checks for poles in the
denominator. For each of these poles, the integral is reevaluated, and
the final integration result is given in terms of a Piecewise.
Examples
========
>>> from diofant.core import symbols
>>> from diofant.functions import cos
>>> from diofant.integrals.heurisch import heurisch, heurisch_wrapper
>>> n, x = symbols('n x')
>>> heurisch(cos(n*x), x)
sin(n*x)/n
>>> heurisch_wrapper(cos(n*x), x)
Piecewise((x, Eq(n, 0)), (sin(n*x)/n, true))
See Also
========
diofant.integrals.heurisch.heurisch
"""
from diofant.solvers.solvers import solve, denoms
f = sympify(f)
if x not in f.free_symbols:
return f * x
res = heurisch(f, x, rewrite, hints, mappings, retries, degree_offset,
unnecessary_permutations)
if not isinstance(res, Basic):
return res
# We consider each denominator in the expression, and try to find
# cases where one or more symbolic denominator might be zero. The
# conditions for these cases are stored in the list slns.
slns = []
for d in denoms(res):
try:
slns += solve(d, dict=True, exclude=(x, ))
except NotImplementedError:
pass
if not slns:
return res
slns = list(uniq(slns))
# Remove the solutions corresponding to poles in the original expression.
slns0 = []
for d in denoms(f):
try:
slns0 += solve(d, dict=True, exclude=(x, ))
except NotImplementedError:
pass
slns = [s for s in slns if s not in slns0]
if not slns:
return res
if len(slns) > 1:
eqs = []
for sub_dict in slns:
eqs.extend([Eq(key, value) for key, value in sub_dict.items()])
slns = solve(eqs, dict=True, exclude=(x, )) + slns
# For each case listed in the list slns, we reevaluate the integral.
pairs = []
for sub_dict in slns:
expr = heurisch(f.subs(sub_dict), x, rewrite, hints, mappings, retries,
degree_offset, unnecessary_permutations)
cond = And(*[Eq(key, value) for key, value in sub_dict.items()])
pairs.append((expr, cond))
pairs.append((heurisch(f, x, rewrite, hints, mappings, retries,
degree_offset, unnecessary_permutations), True))
return Piecewise(*pairs)