Add a horrible test case

src/curve.m

+% -*- mode:octave -*-
+
+clear all
+close all
+
+if exist('graphics_toolkit','file') graphics_toolkit('fltk') end
+
+A=[
+   1 0
+   0 1
+];
+b=[
+   1
+   2.5
+];
+
+x = -.1:.005:.4;
+y = .9:.005:1.1;
+[X, Y] = meshgrid(x,y);
+xlabel('x')
+ylabel('y')
+
+tic
+for i=1:length(y)
+  in = [ X(i,:); Y(i,:) ];
+  f(i,:) = duneevaluate(A,b, 'S', in);
+end
+clear X Y;
+toc
+
+surf(x, y, f)
+hold on;
+
+steps = 1100;
+vecs = zeros(steps + 1, 2);
+diffs = zeros(steps, 2);
+
+vecs(1,:) = [0; 0]; % So that we can always calculate a difference
+vecs(2,:) = [0; 1]; % Start
+
+for j = 2:steps+1 % Something random
+    % Zero is code for 'SteepFunctionNonsmooth'
+    vecs(j+1,:) = duneminimise(A,b, 'S', vecs(j,:));
+    diffs(j,:) = vecs(j+1,:) - vecs(j,:);
+    line([vecs(j,1) vecs(j+1,1)], ...
+	 [vecs(j,2) vecs(j+1,2)], ...
+       [duneevaluate(A,b, 'S', vecs(j,:)') duneevaluate(A,b, 'S', vecs(j+1,:)')], ...
+       'color', 'y');
+end
+
+axis tight;
+xlabel x;
+ylabel y;
+hold off;
+