polys: fix sorting of real roots

Correct fix of sympy/sympy#20902
diofant · Feb 5, 2021 · d8c2efe · d8c2efe
1 parent ae088e8
commit d8c2efe
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Showing 3 changed files with 2 additions and 2 deletions.
diff --git a/diofant/polys/rootisolation.py b/diofant/polys/rootisolation.py
@@ -859,7 +859,7 @@ def as_tuple(self):
 
     def is_disjoint(self, other):
         """Return ``True`` if two isolation intervals are disjoint."""
-        return self.b <= other.a or other.b <= self.a
+        return self.b < other.a or other.b < self.a
 
     def refine(self):
         """Perform one step of real root refinement algorithm."""

diff --git a/diofant/solvers/inequalities.py b/diofant/solvers/inequalities.py
@@ -206,7 +206,6 @@ def solve_poly_inequality(poly, rel):
             raise NotImplementedError(f"Couldn't determine truth value of {t}")
 
     reals, intervals = poly.real_roots(multiple=False), []
-    reals = sorted(reals, key=lambda r: r[0])
 
     if rel == '==':
         for root, _ in reals:

diff --git a/diofant/tests/polys/test_rootoftools.py b/diofant/tests/polys/test_rootoftools.py
@@ -338,6 +338,7 @@ def test_RootOf_real_roots():
     assert (x**5 + x + 1).as_poly().real_roots(radicals=False) == [RootOf(
         x**3 - x**2 + 1, 0)]
     assert (x**7 - 0.1*x + 1).as_poly(x).real_roots() == [RootOf(10*x**7 - x + 10, 0)]
+    assert (x**4 - 3*x**3 + 6*x - 4).as_poly().real_roots() == [-sqrt(2), 1, sqrt(2), 2]
 
 
 def test_RootOf_all_roots():