--- a/+multiblock/DiffOp.m	Wed Jul 25 18:53:07 2018 -0700
+++ b/+multiblock/DiffOp.m	Thu Jul 26 10:53:05 2018 -0700
@@ -10,13 +10,13 @@
     end
 
     methods
-        function obj = DiffOp(doHand, grid, order, doParam)
+        function obj = DiffOp(doHand, g, order, doParam)
             %  doHand -- may either be a function handle or a cell array of
             %            function handles for each grid. The function handle(s)
             %            should be on the form do = doHand(grid, order, ...)
             %            Additional parameters for each doHand may be provided in
             %            the doParam input.
-            %    grid -- a multiblock grid
+            %       g -- a multiblock grid
             %   order -- integer specifying the order of accuracy
             % doParam -- may either be a cell array or a cell array of cell arrays
             %            for each block. If it is a cell array with length equal
@@ -26,9 +26,9 @@
             %            extra parameters to all doHand: doHand(..., doParam{:})
             default_arg('doParam', [])
 
-            [getHand, getParam] = parseInput(doHand, grid, doParam);
+            [getHand, getParam] = parseInput(doHand, g, doParam);
 
-            nBlocks = grid.nBlocks();
+            nBlocks = g.nBlocks();
 
             obj.order = order;
 
@@ -40,7 +40,7 @@
                 if ~iscell(p)
                     p = {p};
                 end
-                obj.diffOps{i} = h(grid.grids{i}, order, p{:});
+                obj.diffOps{i} = h(g.grids{i}, order, p{:});
             end
 
 
@@ -65,7 +65,7 @@
 
             for i = 1:nBlocks
                 for j = 1:nBlocks
-                    intf = grid.connections{i,j};
+                    intf = g.connections{i,j};
                     if isempty(intf)
                         continue
                     end
@@ -81,15 +81,15 @@
                 end
             end
             obj.D = blockmatrix.toMatrix(D);
-            obj.grid = grid;
+            obj.grid = g;
 
 
-            function [getHand, getParam] = parseInput(doHand, grid, doParam)
-                if ~isa(grid, 'multiblock.Grid')
+            function [getHand, getParam] = parseInput(doHand, g, doParam)
+                if ~isa(g, 'multiblock.Grid')
                     error('multiblock:DiffOp:DiffOp:InvalidGrid', 'Requires a multiblock grid.');
                 end
 
-                if iscell(doHand) && length(doHand) == grid.nBlocks()
+                if iscell(doHand) && length(doHand) == g.nBlocks()
                     getHand = @(i)doHand{i};
                 elseif isa(doHand, 'function_handle')
                     getHand = @(i)doHand;
@@ -109,7 +109,7 @@
 
                 % doParam is a non-empty cell-array
 
-                if length(doParam) == grid.nBlocks() && all(cellfun(@iscell, doParam))
+                if length(doParam) == g.nBlocks() && all(cellfun(@iscell, doParam))
                     % doParam is a cell-array of cell-arrays
                     getParam = @(i)doParam{i};
                     return
@@ -148,6 +148,27 @@
             end
         end
 
+        function op = getBoundaryQuadrature(obj, boundary)
+            opName = 'H';
+            switch class(boundary)
+                case 'cell'
+                    localOpName = [opName '_' boundary{2}];
+                    blockId = boundary{1};
+                    op = obj.diffOps{blockId}.(localOpName);
+
+                    return
+                case 'multiblock.BoundaryGroup'
+                    N = length(boundary);
+                    H_bm = cell(N,N);
+                    for i = 1:N
+                        H_bm{i,i} = obj.getBoundaryQuadrature(boundary{i});
+                    end
+                    op = blockmatrix.toMatrix(H_bm);
+                otherwise
+                    error('Unknown boundary indentifier')
+            end
+        end
+
         % Creates the closure and penalty matrix for a given boundary condition,
         %    boundary -- the name of the boundary on the form {id,name} where
         %                id is the number of a block and name is the name of a