--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+multiblock/LaplaceSquared.m	Wed Feb 13 20:52:14 2019 +0100
@@ -0,0 +1,105 @@
+classdef LaplaceSquared < scheme.Scheme
+    properties
+        grid
+        order
+        laplaceDiffOp
+
+        D
+        H
+        Hi
+
+        a,b
+    end
+
+    methods
+        % Discretisation of a*nabla*b*nabla
+        function obj = LaplaceSquared(g, order, a, b, opGen)
+            default_arg('order', 4);
+            default_arg('a', 1);
+            default_arg('b', 1);
+            default_arg('opGen', @sbp.D4Variable);
+
+            if isscalar(a)
+                a = grid.evalOn(g, a);
+            end
+
+            if isscalar(b)
+                b = grid.evalOn(g, b);
+            end
+
+            obj.grid = g;
+            obj.order = order;
+            obj.a = a;
+            obj.b = b;
+
+            obj.laplaceDiffOp = multiblock.Laplace(g, order, 1, 1, opGen);
+
+            obj.H = obj.laplaceDiffOp.H;
+            obj.Hi = spdiag(1./diag(obj.H));
+
+            A = spdiag(a);
+            B = spdiag(b);
+
+            D_laplace = obj.laplaceDiffOp.D;
+            obj.D = A*D_laplace*B*D_laplace;
+        end
+
+        function s = size(obj)
+            s = size(obj.laplaceDiffOp);
+        end
+
+        function op = getBoundaryOperator(obj, opName, boundary)
+            switch opName
+                case 'e'
+                    op = getBoundaryOperator(obj.laplaceDiffOp, 'e', boundary);
+                case 'd1'
+                    op = getBoundaryOperator(obj.laplaceDiffOp, 'd', boundary);
+                case 'd2'
+                    e = getBoundaryOperator(obj.laplaceDiffOp, 'e', boundary);
+                    op = (e'*obj.laplaceDiffOp.D)';
+                case 'd3'
+                    d1 = getBoundaryOperator(obj.laplaceDiffOp, 'd', boundary);
+                    op = (d1'*spdiag(obj.b)*obj.laplaceDiffOp.D)';
+            end
+        end
+
+        function op = getBoundaryQuadrature(obj, boundary)
+            op = getBoundaryQuadrature(obj.laplaceDiffOp, boundary);
+        end
+
+        function [closure, penalty] = boundary_condition(obj,boundary,type) % TODO: Change name to boundaryCondition
+            switch type
+                case 'e'
+                    error('Bc of type ''e'' not implemented')
+                case 'd1'
+                    error('Bc of type ''d1'' not implemented')
+                case 'd2'
+                    e = obj.getBoundaryOperator('e', boundary);
+                    d1 = obj.getBoundaryOperator('d1', boundary);
+                    d2 = obj.getBoundaryOperator('d2', boundary);
+                    H_b = obj.getBoundaryQuadrature(boundary);
+
+                    A = spdiag(obj.a);
+                    B_b = spdiag(e'*obj.b);
+
+                    tau = obj.Hi*A*d1*B_b*H_b;
+                    closure =  tau*d2';
+                    penalty = -tau;
+                case 'd3'
+                    e = obj.getBoundaryOperator('e', boundary);
+                    d3 = obj.getBoundaryOperator('d3', boundary);
+                    H_b = obj.getBoundaryQuadrature(boundary);
+
+                    A = spdiag(obj.a);
+
+                    tau = -obj.Hi*A*e*H_b;
+                    closure =  tau*d3';
+                    penalty = -tau;
+            end
+        end
+
+        function [closure, penalty] = interface(obj,boundary,neighbour_scheme,neighbour_boundary)
+            error('Not implemented')
+        end
+    end
+end