--- a/+scheme/Schrodinger.m	Sat Jan 12 13:35:19 2019 -0800
+++ b/+scheme/Schrodinger.m	Sat Jan 12 13:44:08 2019 -0800
@@ -67,7 +67,8 @@
             default_arg('type','dirichlet');
             default_arg('data',0);
 
-            [e,d,s] = obj.get_boundary_ops(boundary);
+            [e, d] = obj.getBoundaryOperator({'e', 'd'}, boundary);
+            s = obj.getBoundarySign(boundary);
 
             switch type
                 % Dirichlet boundary condition
@@ -93,8 +94,11 @@
         function [closure, penalty] = interface(obj, boundary, neighbour_scheme, neighbour_boundary, type)
             % u denotes the solution in the own domain
             % v denotes the solution in the neighbour domain
-            [e_u,d_u,s_u] = obj.get_boundary_ops(boundary);
-            [e_v,d_v,s_v] = neighbour_scheme.get_boundary_ops(neighbour_boundary);
+            [e_u, d_u] = obj.getBoundaryOperator({'e', 'd'}, boundary);
+            s_u = obj.getBoundarySign(boundary);
+
+            [e_v, d_v] = neighbour_scheme.getBoundaryOperator({'e', 'd'}, neighbour_boundary);
+            s_v = neighbour_scheme.getBoundarySign(neighbour_boundary);
 
             a =  -s_u* 1/2 * 1i ;
             b =  a';
@@ -106,18 +110,50 @@
             penalty = obj.Hi * (-tau*e_v' - sig*d_v');
         end
 
-        % Ruturns the boundary ops and sign for the boundary specified by the string boundary.
-        % The right boundary is considered the positive boundary
-        function [e,d,s] = get_boundary_ops(obj,boundary)
+        % Returns the boundary operator op for the boundary specified by the string boundary.
+        % op        -- string or a cell array of strings
+        % boundary  -- string
+        function varargout = getBoundaryOperator(obj, op, boundary)
+
+            if ~iscell(op)
+                op = {op};
+            end
+
+            for i = 1:numel(op)
+                switch op{i}
+                case 'e'
+                    switch boundary
+                    case 'l'
+                        e = obj.e_l;
+                    case 'r'
+                        e = obj.e_r;
+                    otherwise
+                        error('No such boundary: boundary = %s',boundary);
+                    end
+                    varargout{i} = e;
+
+                case 'd'
+                    switch boundary
+                    case 'l'
+                        d = obj.d1_l;
+                    case 'r'
+                        d = obj.d1_r;
+                    otherwise
+                        error('No such boundary: boundary = %s',boundary);
+                    end
+                    varargout{i} = d;
+                end
+            end
+        end
+
+        % Returns the boundary sign. The right boundary is considered the positive boundary
+        % boundary -- string
+        function s = getBoundarySign(obj, boundary)
             switch boundary
-                case 'l'
-                    e = obj.e_l;
-                    d = obj.d1_l;
+                case {'r'}
+                    s = 1;
+                case {'l'}
                     s = -1;
-                case 'r'
-                    e = obj.e_r;
-                    d = obj.d1_r;
-                    s = 1;
                 otherwise
                     error('No such boundary: boundary = %s',boundary);
             end