--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+sbp/D4Compatible.m	Fri Sep 23 10:40:12 2016 +0200
@@ -0,0 +1,75 @@
+classdef D4Compatible < sbp.OpSet
+    properties
+        D1 % SBP operator approximating first derivative
+        H % Norm matrix
+        HI % H^-1
+        Q % Skew-symmetric matrix
+        e_l % Left boundary operator
+        e_r % Right boundary operator
+        D2 % SBP operator for second derivative
+        M % Norm matrix, second derivative
+        d1_l % Left boundary first derivative
+        d1_r % Right boundary first derivative
+        D3 % SBP operator for third derivative
+        Q3 % Skew-symmetric matrix in third derivative
+        d2_l % Left boundary second derivative
+        d2_r % Right boundary second derivative
+        D4 % SBP operator for fourth derivative
+        M4 % Norm matrix, fourth derivative
+        d3_l % Left boundary third derivative
+        d3_r % Right boundary third derivative
+        m % Number of grid points.
+        h % Step size
+        x % grid
+        borrowing % Struct with borrowing limits for different norm matrices
+    end
+
+
+
+    methods
+        function obj = D4Compatible(m,lim,order)
+            
+            
+            x_l = lim{1};
+            x_r = lim{2};
+            L = x_r-x_l;
+            obj.h = L/(m-1);
+            obj.x = linspace(x_l,x_r,m)';
+
+            if order == 2
+                [obj.H, obj.HI, obj.D1, obj.D4, obj.e_l, obj.e_r, obj.M4,...
+                 obj.Q, obj.d2_l, obj.d2_r, obj.d3_l, obj.d3_r,...
+                    obj.d1_l, obj.d1_r] =...
+                    sbp.implementations.d4_compatible_2(m,obj.h);
+                obj.borrowing.N.S2 = 0.7500;
+                obj.borrowing.N.S3 = 0.3000;
+            elseif order == 4
+                [obj.H, obj.HI, obj.D1, obj.D4, obj.e_l, obj.e_r, obj.M4,...
+                 obj.Q, obj.d2_l, obj.d2_r, obj.d3_l, obj.d3_r,...
+                    obj.d1_l, obj.d1_r] =...
+                    sbp.implementations.d4_compatible_4(m,obj.h);
+                obj.borrowing.N.S2 = 0.4210;
+                obj.borrowing.N.S3 = 0.7080;
+            elseif order == 6
+                [obj.H, obj.HI, obj.D1, obj.D4, obj.e_l, obj.e_r, obj.M4,...
+                 obj.Q, obj.d2_l, obj.d2_r, obj.d3_l, obj.d3_r,...
+                    obj.d1_l, obj.d1_r] =...
+                    sbp.implementations.d4_compatible_6(m,obj.h);
+                obj.borrowing.N.S2 = 0.06925;
+                obj.borrowing.N.S3 = 0.05128;
+            else
+                error('Invalid operator order.');
+            end
+
+            obj.m = m;
+
+            obj.D2 = [];
+            obj.D3 = [];
+
+
+        end
+    end
+
+
+
+end
\ No newline at end of file