Merge pull request sympy#1438 from asmeurer/nsolve-fix

nsolve uses free_symbols instead of atoms(Symbol) (issue 3309)

sympy/solvers/solvers.py

@@ -2034,10 +2034,10 @@ def nsolve(*args, **kwargs):
         if isinstance(f, Equality):
             f = f.lhs - f.rhs
         f = f.evalf()
-        atoms = f.atoms(Symbol)
+        syms = f.free_symbols
         if fargs is None:
-            fargs = atoms.copy().pop()
-        if not (len(atoms) == 1 and (fargs in atoms or fargs[0] in atoms)):
+            fargs = syms.copy().pop()
+        if not (len(syms) == 1 and (fargs in syms or fargs[0] in syms)):
             raise ValueError(filldedent('''
                 expected a one-dimensional and numerical function'''))
 

sympy/solvers/tests/test_numeric.py

@@ -1,8 +1,8 @@
-from sympy import Eq, Matrix, pi, sin, sqrt, Symbol
+from sympy import Eq, Matrix, pi, sin, sqrt, Symbol, Integral, Piecewise, symbols
 from sympy.mpmath import mnorm, mpf
 from sympy.solvers import nsolve
 from sympy.utilities.lambdify import lambdify
-from sympy.utilities.pytest import raises
+from sympy.utilities.pytest import raises, XFAIL
 
 def test_nsolve():
     # onedimensional
@@ -43,3 +43,12 @@ def getroot(x0):
     a = Symbol('a')
     assert nsolve(1/(0.001 + a)**3 - 6/(0.9 - a)**3, a, 0.3).ae(
         mpf('0.31883011387318591'))
+
+def test_issue_3309():
+    x = Symbol('x')
+    assert nsolve(Piecewise((x,x<1),(x**2,True)),x,2) == 0.0
+
+@XFAIL
+def test_issue_3309_fail():
+    x, y = symbols('x y')
+    assert nsolve(Integral(x*y,(x,0,5)),y,2) == 0.0