From 852612225256bda771c0b546f134a99e0630aedd Mon Sep 17 00:00:00 2001
From: Ondrej Certik <ondrej@certik.cz>
Date: Wed, 12 Dec 2007 22:46:21 +0100
Subject: [PATCH] .subs() in Relational implemented, tests written

---
 sympy/core/relational.py      |  3 +++
 sympy/core/tests/test_subs.py | 17 ++++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/sympy/core/relational.py b/sympy/core/relational.py
index 1b528cb..b9e3199 100644
--- a/sympy/core/relational.py
+++ b/sympy/core/relational.py
@@ -44,6 +44,9 @@ class Relational(Basic, NoRelMeths):
             return '(%s)' % r
         return r
 
+    def subs(self, old, new):
+        return self.lhs.subs(old, new) == self.rhs.subs(old, new)
+
 class Equality(Relational):
 
     rel_op = '=='
diff --git a/sympy/core/tests/test_subs.py b/sympy/core/tests/test_subs.py
index e6f3329..d55245c 100644
--- a/sympy/core/tests/test_subs.py
+++ b/sympy/core/tests/test_subs.py
@@ -4,7 +4,8 @@ sys.path.append(".")
 import py
 
 import sympy as g
-from sympy import Symbol, Wild, sin, cos, exp, pi, Function, Derivative
+from sympy import Symbol, Wild, sin, cos, exp, pi, Function, Derivative, abc, \
+        Integer
 from sympy.utilities.pytest import XFAIL
 
 def test_subs():
@@ -97,3 +98,17 @@ def test_deriv_sub_bug3():
     pat = Derivative(f(x), x, x)
     assert pat.subs(y, y**2) == Derivative(f(x), x, x)
     assert pat.subs(y, y**2) != Derivative(f(x), x)
+
+def test_equality_subs1():
+    f = Function("f")
+    x = abc.x
+    eq = f(x)**2 == x
+    res = Integer(16) == x
+    assert eq.subs(f(x), 4) == res
+
+def test_equality_subs2():
+    f = Function("f")
+    x = abc.x
+    eq = f(x)**2 == 16
+    assert eq.subs(f(x), 3) == False
+    assert eq.subs(f(x), 4) == True
-- 
2.11.4.GIT