Merge ce1ac90 into 0e5a81b

essm/variables/_core.py

@@ -97,6 +97,12 @@ def __delitem__(cls, expr):
             if expr in registry:
                 del registry[expr]
 
+    @property
+    def function(cls):
+        """Return a symbolic function."""
+        from sage.symbolic.function_factory import function_factory
+        return function_factory(cls.name + '_function')
+
 
 @six.add_metaclass(VariableMeta)
 class Variable(object):
@@ -129,6 +135,10 @@ def __new__(
         self.definition = definition
         return self
 
+    def __call__(self, *args):
+        """Return function."""
+        return self.definition.function(*args)
+
     @property
     def __doc__(self):
         return self.definition.__doc__