--- a/+sbp/+implementations/d2_variable_2.m	Thu Feb 17 18:55:11 2022 +0100
+++ b/+sbp/+implementations/d2_variable_2.m	Thu Mar 10 16:54:26 2022 +0100
@@ -27,7 +27,7 @@
     diags   = -1:1;
     stencil = [-1/2 0 1/2];
     D1 = stripeMatrix(stencil, diags, m);
-    
+
     D1(1,1)=-1;D1(1,2)=1;D1(m,m-1)=-1;D1(m,m)=1;
     D1(m,m-1)=-1;D1(m,m)=1;
     D1=D1/h;
@@ -40,7 +40,7 @@
     scheme_radius = (scheme_width-1)/2;
     r = (1+scheme_radius):(m-scheme_radius);
 
-    function D2 = D2_fun(c)
+    function [D2, B] = D2_fun(c)
 
         Mm1 = -c(r-1)/2 - c(r)/2;
         M0  =  c(r-1)/2 + c(r)   + c(r+1)/2;
@@ -54,6 +54,8 @@
         M=M/h;
 
         D2=HI*(-M-c(1)*e_l*d1_l'+c(m)*e_r*d1_r');
+        B = HI*M;
     end
     D2 = @D2_fun;
+
 end
\ No newline at end of file