--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/+time/Timestepper.m	Thu Sep 17 10:12:50 2015 +0200
@@ -0,0 +1,81 @@
+classdef Timestepper < handle
+    properties (Abstract)
+        t
+        k
+        n
+    end
+
+    methods (Abstract)
+         [v,t] = getV(obj)
+         obj = step(obj)
+    end
+
+
+    methods
+        function [v,t] = stepN(obj,n,progress_bar)
+
+            if progress_bar && n > 1500
+                n1000 = floor(n/1000);
+
+                s = util.replace_string('','   %d %%',0);
+                for i=1:n
+                    obj.step();
+                    if mod(i,n1000) == 0
+                    s = util.replace_string(s,'   %.2f %%',i/n*100);
+                    end
+                end
+                s = util.replace_string(s,'');
+            else
+                for i=1:n
+                    obj.step();
+                end
+            end
+            v = obj.getV;
+            t = obj.t;
+        end
+
+        function [v,t] = evolve(obj, tend, progress_bar)
+            default_arg('progress_bar',false)
+            if progress_bar
+                obj.evolve_with_progress(tend);
+            else
+                obj.evolve_without_progress(tend);
+            end
+            v = obj.getV;
+            t = obj.t;
+        end
+
+        function evolve_with_progress(obj, tend)
+            dt = tend-obj.t;
+            n = floor(dt/obj.k);
+            n1000 = floor(n/1000);
+
+            i = 0;
+            s = util.replace_string('','   %d %%',0);
+            while obj.t < tend - obj.k/100
+                obj.step();
+
+                i = i + 1;
+                if mod(i,n1000) == 0
+                    s = util.replace_string(s,'   %.2f %%',i/n*100);
+                end
+            end
+
+            % if t < tend
+            %     v = rk4.rungekutta_4(v, t, tend-t,F);
+            % end
+
+            s = util.replace_string(s,'');
+        end
+
+        function evolve_without_progress(obj, tend)
+            while obj.t < tend - obj.k/100
+                obj.step();
+            end
+
+            % if t < tend
+            %     v = rk4.rungekutta_4(v, t, tend-t,F);
+            % end
+        end
+    end
+end
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