diff --git a/mis_builder/models/simple_array.py b/mis_builder/models/simple_array.py
new file mode 100644
index 00000000..e05702d3
--- /dev/null
+++ b/mis_builder/models/simple_array.py
@@ -0,0 +1,103 @@
+""" A trivial immutable array that supports basic arithmetic operations.
+
+>>> a = SimpleArray((1.0, 2.0, 3.0))
+>>> b = SimpleArray((4.0, 5.0, 6.0))
+>>> t  = (4.0, 5.0, 6.0)
+>>> +a
+SimpleArray((1.0, 2.0, 3.0))
+>>> -a
+SimpleArray((-1.0, -2.0, -3.0))
+>>> a + b
+SimpleArray((5.0, 7.0, 9.0))
+>>> b + a
+SimpleArray((5.0, 7.0, 9.0))
+>>> a + t
+SimpleArray((5.0, 7.0, 9.0))
+>>> t + a
+SimpleArray((5.0, 7.0, 9.0))
+>>> a - b
+SimpleArray((-3.0, -3.0, -3.0))
+>>> a - t
+SimpleArray((-3.0, -3.0, -3.0))
+>>> t - a
+SimpleArray((3.0, 3.0, 3.0))
+>>> a * b
+SimpleArray((4.0, 10.0, 18.0))
+>>> b * a
+SimpleArray((4.0, 10.0, 18.0))
+>>> a * t
+SimpleArray((4.0, 10.0, 18.0))
+>>> t * a
+SimpleArray((4.0, 10.0, 18.0))
+>>> a / b
+SimpleArray((0.25, 0.4, 0.5))
+>>> b / a
+SimpleArray((4.0, 2.5, 2.0))
+>>> a / t
+SimpleArray((0.25, 0.4, 0.5))
+>>> t / a
+SimpleArray((4.0, 2.5, 2.0))
+"""
+
+import operator
+
+
+__all__ = ['SimpleArray']
+
+
+class SimpleArray(tuple):
+
+    def _op(self, op, other):
+        if isinstance(other, tuple):
+            if len(other) != len(self):
+                raise TypeError("tuples must have same length for %s" % op)
+            return SimpleArray(map(op, self, other))
+        return NotImplemented
+
+    def __add__(self, other):
+        return self._op(operator.add, other)
+
+    __radd__ = __add__
+
+    def __pos__(self):
+        return SimpleArray(map(operator.pos, self))
+
+    def __neg__(self):
+        return SimpleArray(map(operator.neg, self))
+
+    def __sub__(self, other):
+        return self._op(operator.sub, other)
+
+    def __rsub__(self, other):
+        return SimpleArray(other)._op(operator.sub, self)
+
+    def __mul__(self, other):
+        return self._op(operator.mul, other)
+
+    __rmul__ = __mul__
+
+    def __div__(self, other):
+        return self._op(operator.div, other)
+
+    def __floordiv__(self, other):
+        return self._op(operator.floordiv, other)
+
+    def __truediv__(self, other):
+        return self._op(operator.truediv, other)
+
+    def __rdiv__(self, other):
+        return SimpleArray(other)._op(operator.div, self)
+
+    def __rfloordiv__(self, other):
+        return SimpleArray(other)._op(operator.floordiv, self)
+
+    def __rtruediv__(self, other):
+        return SimpleArray(other)._op(operator.truediv, self)
+
+    def __repr__(self):
+        return "SimpleArray(%s)" % tuple.__repr__(self)
+
+
+if __name__ == '__main__':
+    import doctest
+    doctest.testmod()