add lab1 and lab2 exercises

lab1/switch.smv

@@ -0,0 +1,25 @@
+MODULE main
+    -- Model of the switch
+    IVAR
+        press   : boolean;
+    VAR
+        mode    : {on, off};
+        x       : 0..15;
+    ASSIGN
+        init(mode) := off;
+        next(mode) := case
+            mode = off & press              : on;
+            mode = on & (press | x >= 10)   : off;
+            TRUE                            : mode;
+        esac;
+        init(x) := 0;
+        next(x) := case
+            mode = on & next(mode) = off    : 0;
+            mode = on & x < 10              : x + 1;
+            TRUE                            : x;
+        esac;
+        
+INVARSPEC x <= 10;
+INVARSPEC mode = off -> x = 0;
+INVARSPEC x < 10;
+INVARSPEC mode = off;