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Support solving for Dummy symbols in linsolve #9668

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merged 1 commit into from Jul 17, 2015
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Support solving for Dummy symbols in linsolve #9668

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7 changes: 6 additions & 1 deletion sympy/solvers/solveset.py
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Expand Up @@ -1140,7 +1140,12 @@ def linsolve(system, *symbols):
if hasattr(symbols[0], '__iter__'):
symbols = symbols[0]

if not type(symbols[0]) == Symbol:
try:
sym = symbols[0].is_Symbol
except AttributeError:
sym = False

if not sym:
raise ValueError('Symbols or iterable of symbols must be given as '
'second argument, not type %s: %s' % (type(symbols[0]), symbols[0]))

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18 changes: 13 additions & 5 deletions sympy/solvers/tests/test_solveset.py
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Expand Up @@ -846,17 +846,17 @@ def test_linsolve():
# Test for different input forms

M = Matrix([[1, 2, 1, 1, 7], [1, 2, 2, -1, 12], [2, 4, 0, 6, 4]])
system = A, b = M[:, :-1], M[:, -1]
system1 = A, b = M[:, :-1], M[:, -1]
Eqns = [x1 + 2*x2 + x3 + x4 - 7, x1 + 2*x2 + 2*x3 - x4 - 12,
2*x1 + 4*x2 + 6*x4 - 4]

sol = FiniteSet((-2*x2 - 3*x4 + 2, x2, 2*x4 + 5, x4))
assert linsolve(M, (x1, x2, x3, x4)) == sol
assert linsolve(Eqns, (x1, x2, x3, x4)) == sol
assert linsolve(system, (x1, x2, x3, x4)) == sol
assert linsolve(system1, (x1, x2, x3, x4)) == sol

# raise ValueError if no symbols are given
raises(ValueError, lambda: linsolve(system))
raises(ValueError, lambda: linsolve(system1))

# raise ValueError if, A & b is not given as tuple
raises(ValueError, lambda: linsolve(A, b, x1, x2, x3, x4))
Expand All @@ -868,10 +868,18 @@ def test_linsolve():
a, b, c, d, e, f = symbols('a, b, c, d, e, f')
A = Matrix([[a, b], [c, d]])
B = Matrix([[e], [f]])
system = (A, B)
system2 = (A, B)
sol = FiniteSet((-b*(f - c*e/a)/(a*(d - b*c/a)) + e/a,
(f - c*e/a)/(d - b*c/a)))
assert linsolve(system, [x, y]) == sol
assert linsolve(system2, [x, y]) == sol

# Test for Dummy Symbols issue #9667
x1 = Dummy('x1')
x2 = Dummy('x2')
x3 = Dummy('x3')
x4 = Dummy('x4')

assert linsolve(system1, x1, x2, x3, x4) == FiniteSet((-2*x2 - 3*x4 + 2, x2, 2*x4 + 5, x4))


def test_issue_9556():
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