def _roots_trivial(cls, poly, radicals):
"""Compute roots in linear, quadratic and binomial cases. """
if poly.degree() == 1:
return roots_linear(poly)
if not radicals:
return
if poly.degree() == 2:
return roots_quadratic(poly)
elif poly.length() == 2 and poly.TC():
return roots_binomial(poly)
else:
return
def test_roots_linear():
assert roots_linear(Poly(2 * x + 1, x)) == [-Rational(1, 2)]
def test_roots_linear():
assert roots_linear((2 * x + 1).as_poly()) == [-Rational(1, 2)]
def test_roots_linear():
assert roots_linear(Poly(2*x + 1, x)) == [-Rational(1, 2)]
def __new__(cls, expr, func=None, x=None, auto=True, quadratic=False):
"""Construct a new ``RootSum`` instance carrying all roots of a polynomial. """
coeff, poly = cls._transform(expr, x)
if not poly.is_univariate:
raise MultivariatePolynomialError(
"only univariate polynomials are allowed")
if func is None:
func = Lambda(poly.gen, poly.gen)
else:
try:
is_func = func.is_Function
except AttributeError:
is_func = False
if is_func and 1 in func.nargs:
if not isinstance(func, Lambda):
func = Lambda(poly.gen, func(poly.gen))
else:
raise ValueError("expected a univariate function, got %s" %
func)
var, expr = func.variables[0], func.expr
if coeff is not S.One:
expr = expr.subs(var, coeff * var)
deg = poly.degree()
if not expr.has(var):
return deg * expr
if expr.is_Add:
add_const, expr = expr.as_independent(var)
else:
add_const = S.Zero
if expr.is_Mul:
mul_const, expr = expr.as_independent(var)
else:
mul_const = S.One
func = Lambda(var, expr)
rational = cls._is_func_rational(poly, func)
(_, factors), terms = poly.factor_list(), []
for poly, k in factors:
if poly.is_linear:
term = func(roots_linear(poly)[0])
elif quadratic and poly.is_quadratic:
term = sum(map(func, roots_quadratic(poly)))
else:
if not rational or not auto:
term = cls._new(poly, func, auto)
else:
term = cls._rational_case(poly, func)
terms.append(k * term)
return mul_const * Add(*terms) + deg * add_const