From b3c8ea7f26d6b092f467b765925745b8603914d9 Mon Sep 17 00:00:00 2001
From: Michael Bynum <mlbynum@sandia.gov>
Date: Thu, 25 Feb 2021 11:10:32 -0700
Subject: [PATCH] inequality function should work with floats

---
 pyomo/core/base/constraint.py     | 18 ++++++++++--------
 pyomo/core/tests/unit/test_con.py | 21 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/pyomo/core/base/constraint.py b/pyomo/core/base/constraint.py
index 60f0dace41b..3c872080088 100644
--- a/pyomo/core/base/constraint.py
+++ b/pyomo/core/base/constraint.py
@@ -601,18 +601,20 @@ def set_value(self, expr):
                         "using '<=', '>=', or '=='."
                         % (self.name))
 
-                if not expr.arg(1).is_potentially_variable():
+                arg0 = as_numeric(expr.arg(0))
+                arg1 = as_numeric(expr.arg(1))
+                if not arg1.is_potentially_variable():
                     self._lower = None
-                    self._body  = expr.arg(0)
-                    self._upper = as_numeric(expr.arg(1))
-                elif not expr.arg(0).is_potentially_variable():
-                    self._lower = as_numeric(expr.arg(0))
-                    self._body  = expr.arg(1)
+                    self._body  = arg0
+                    self._upper = arg1
+                elif not arg0.is_potentially_variable():
+                    self._lower = arg0
+                    self._body  = arg1
                     self._upper = None
                 else:
                     self._lower = None
-                    self._body = expr.arg(0)
-                    self._body -= expr.arg(1)
+                    self._body = arg0
+                    self._body -= arg1
                     self._upper = ZeroConstant
 
 
diff --git a/pyomo/core/tests/unit/test_con.py b/pyomo/core/tests/unit/test_con.py
index f7e919a13de..9f0855ecbec 100644
--- a/pyomo/core/tests/unit/test_con.py
+++ b/pyomo/core/tests/unit/test_con.py
@@ -568,6 +568,27 @@ def test_mutable_novalue_param_equality(self):
         self.assertEqual(model.c.equality, True)
         model.del_component(model.c)
 
+    def test_inequality(self):
+        m = ConcreteModel()
+        m.x = Var()
+        m.c = Constraint(expr=inequality(lower=-1, body=m.x))
+        self.assertEqual(m.c.lower.value, -1)
+        self.assertIs(m.c.body, m.x)
+        self.assertIs(m.c.upper, None)
+
+        del m.c
+        m.c = Constraint(expr=inequality(body=m.x, upper=1))
+        self.assertIs(m.c.lower, None)
+        self.assertIs(m.c.body, m.x)
+        self.assertEqual(m.c.upper.value, 1)
+
+        del m.c
+        m.c = Constraint(expr=inequality(lower=-1, body=m.x, upper=1))
+        self.assertEqual(m.c.lower.value, -1)
+        self.assertIs(m.c.body, m.x)
+        self.assertEqual(m.c.upper.value, 1)
+
+
 class TestSimpleCon(unittest.TestCase):
 
     def test_set_expr_explicit_multivariate(self):