Merge pull request #19502 from gschintgen/fix-19496-condset-dummy

Fix ConditionSet.dummy_eq() and .as_dummy()

sympy/sets/conditionset.py

@@ -191,8 +191,12 @@ def __new__(cls, sym, condition, base_set=S.UniversalSet):
 
     @property
     def free_symbols(self):
-        s, c, b = self.args
-        return (c.free_symbols - s.free_symbols) | b.free_symbols
+        cond_syms = self.condition.free_symbols - self.sym.free_symbols
+        return cond_syms | self.base_set.free_symbols
+
+    @property
+    def bound_symbols(self):
+        return self.sym.free_symbols
 
     def _contains(self, other):
         return And(
@@ -246,21 +250,3 @@ def _eval_subs(self, old, new):
             # __new__ we *don't* check if 'sym' actually belongs to
             # 'base'. In other words: assumptions are ignored.
             return self.func(self.sym, cond, base)
-
-    def dummy_eq(self, other, symbol=None):
-        if not isinstance(other, self.func):
-            return False
-        if isinstance(self.sym, Symbol) != isinstance(other.sym, Symbol):
-            # this test won't be necessary when unsolved equations
-            # syntax is removed
-            return False
-        if symbol:
-            raise ValueError('symbol arg not supported for ConditionSet')
-        o = other
-        if isinstance(self.sym, Symbol) and isinstance(other.sym, Symbol):
-            # this code will not need to be in an if-block when
-            # the unsolved equations syntax is removed
-            o = other.func(self.sym,
-                other.condition.subs(other.sym, self.sym),
-                other.base_set)
-        return self == o

sympy/sets/tests/test_conditionset.py

@@ -1,6 +1,6 @@
 from sympy.sets import (ConditionSet, Intersection, FiniteSet,
-    EmptySet, Union, Contains, imageset)
-from sympy import (Symbol, Eq, S, Abs, sin, asin, pi, Interval,
+    EmptySet, Union, Contains, ImageSet)
+from sympy import (Symbol, Eq, Ne, S, Abs, sin, asin, pi, Interval,
     And, Mod, oo, Function, Lambda)
 from sympy.testing.pytest import raises, XFAIL, warns_deprecated_sympy
 
@@ -85,6 +85,30 @@ def test_free_symbols():
         ).free_symbols == {z}
     assert ConditionSet(x, Eq(x, 0), FiniteSet(x, z)
         ).free_symbols == {x, z}
+    assert ConditionSet(x, Eq(x, 0), ImageSet(Lambda(y, y**2), S.Integers)
+        ).free_symbols == set()
+
+
+def test_bound_symbols():
+    assert ConditionSet(x, Eq(y, 0), FiniteSet(z)
+        ).bound_symbols == {x}
+    assert ConditionSet(x, Eq(x, 0), FiniteSet(x, y)
+        ).bound_symbols == {x}
+    assert ConditionSet(x, x < 10, ImageSet(Lambda(y, y**2), S.Integers)
+        ).bound_symbols == {x}
+    assert ConditionSet(x, x < 10, ConditionSet(y, y > 1, S.Integers)
+        ).bound_symbols == {x}
+
+
+def test_as_dummy():
+    _0 = Symbol('_0')
+    assert ConditionSet(x, x < 1, Interval(y, oo)
+        ).as_dummy() == ConditionSet(_0, _0 < 1, Interval(y, oo))
+    assert ConditionSet(x, x < 1, Interval(x, oo)
+        ).as_dummy() == ConditionSet(_0, _0 < 1, Interval(x, oo))
+    assert ConditionSet(x, x < 1, ImageSet(Lambda(y, y**2), S.Integers)
+        ).as_dummy() == ConditionSet(
+            _0, _0 < 1, ImageSet(Lambda(_0, _0**2), S.Integers))
 
 
 def test_subs_CondSet():
@@ -132,8 +156,8 @@ def test_subs_CondSet():
 
     # issue 17341
     k = Symbol('k')
-    img1 = imageset(Lambda(k, 2*k*pi + asin(y)), S.Integers)
-    img2 = imageset(Lambda(k, 2*k*pi + asin(S.One/3)), S.Integers)
+    img1 = ImageSet(Lambda(k, 2*k*pi + asin(y)), S.Integers)
+    img2 = ImageSet(Lambda(k, 2*k*pi + asin(S.One/3)), S.Integers)
     assert ConditionSet(x, Contains(
         y, Interval(-1,1)), img1).subs(y, S.One/3).dummy_eq(img2)
 
@@ -154,7 +178,6 @@ def test_dummy_eq():
     assert c.dummy_eq(C(y, y < 1, I))
     assert c.dummy_eq(1) == False
     assert c.dummy_eq(C(x, x < 1, S.Reals)) == False
-    raises(ValueError, lambda: c.dummy_eq(C(x, x < 1, S.Reals), z))
 
     c1 = ConditionSet((x, y), Eq(x + 1, 0) & Eq(x + y, 0), S.Reals)
     c2 = ConditionSet((x, y), Eq(x + 1, 0) & Eq(x + y, 0), S.Reals)
@@ -164,6 +187,16 @@ def test_dummy_eq():
     assert c.dummy_eq(c1) is False
     assert c1.dummy_eq(c) is False
 
+    # issue 19496
+    m = Symbol('m')
+    n = Symbol('n')
+    a = Symbol('a')
+    d1 = ImageSet(Lambda(m, m*pi), S.Integers)
+    d2 = ImageSet(Lambda(n, n*pi), S.Integers)
+    c1 = ConditionSet(x, Ne(a, 0), d1)
+    c2 = ConditionSet(x, Ne(a, 0), d2)
+    assert c1.dummy_eq(c2)
+
 
 def test_contains():
     assert 6 in ConditionSet(x, x > 5, Interval(1, 7))