2012 9 1 Copyright© 2011 IT Planning,Inc All rights reserved. A B C A A B C ON (* 4 ON/OFF . *) let overwrite_mode = ref false let bar_graph = ref true let line_graph = ref false let scatter_diagram = ref false (OCaml) ( ) ON ON OFF OFF ON OFF ON OFF ON ON OFF OFF ON [ ON] ON[ OFF] let on_bargraph_click () = (* *) if !overwrite_mode then bar_graph := not !bar_graph (* *) else if !bar_graph then (