also visualize train position in example

Train/SimpleTrainTrack.mch

@@ -4,7 +4,7 @@ MACHINE TrainTrack
 SETS
   TTDS = {ttd1,ttd2,ttd3}
 CONSTANTS
-  TrackElementNumber, TRACK, TTD_TrackElements
+  TrackElementNumber, TRACK, TTD_TrackElements, train_length
 PROPERTIES
   TrackElementNumber : NATURAL1
 & TRACK = 0..TrackElementNumber
@@ -13,17 +13,23 @@ PROPERTIES
 
 & TrackElementNumber = 30
 & TTD_TrackElements = {ttd1 |-> 0..10 , ttd2 |-> 11..25 , ttd3 |-> 26..30}
+& train_length = 2
 VARIABLES
-  occ
+  occ,
+  train_rear_end
 INVARIANT
-  occ <: TTDS
-INITIALISATION occ := {}
+  occ <: TTDS &
+  train_rear_end : TRACK
+INITIALISATION occ := {} || train_rear_end := 0
 OPERATIONS
   TTD_Occupied(ttd) = PRE ttd:TTDS \ occ THEN
     occ := occ \/ {ttd}
   END;
   TTD_Free(ttd) = PRE ttd:occ THEN
     occ := occ \ {ttd}
+  END;
+  TrainMoveForward = PRE train_rear_end+1:TRACK THEN
+    train_rear_end := train_rear_end + 1
   END
 DEFINITIONS
  "LibrarySVG.def"; // enable to use the external functions in the VisB json file

Train/Track.json

@@ -2,6 +2,13 @@
   "svg":"Track.svg",
   "items":[
   
+    {
+      "id":"train_polygon",
+      "attr":"points",
+      "value":"svg_train(train_rear_end, train_length ,100.0/real(TrackElementNumber+1),1.0,3.0)",
+      "comment":"show train position using a slanted polygon"
+    },
+    
     {
       "id":"track_polyline",
       "attr":"points",
@@ -18,13 +25,13 @@
       "id":"occupied_ttd_polygon",
       "attr":"points",
       "value":"svg_set_polygon(OCC_TE,100.0/real(TrackElementNumber+1),100.0,2.0)",
-      "comment":"show ticks for TTD Limits"
+      "comment":"show occupied TTD zones"
     },
     {
       "id":"cleared_ttd_polygon",
       "attr":"points",
       "value":"svg_set_polygon(FREE_TE,100.0/real(TrackElementNumber+1),100.0,2.0)",
-      "comment":"show ticks for TTD Limits"
+      "comment":"show free TTD zones"
     }
     ],
   "events":[ 
@@ -41,6 +48,13 @@
       "optional" : true,
       "hovers": [{ "attr":"stroke", "enter":"black", "leave":"none"},
                  { "attr":"opacity", "enter":"0.5", "leave":"1.0"}]
+    },
+    {
+      "id":"train_polygon",
+      "event":"TrainMoveForward",
+      "optional" : true,
+      "hovers": [{ "attr":"fill", "enter":"red", "leave":"lightgray"},
+                 { "attr":"stroke-width", "enter":"0.5", "leave":"0.3"}]
     }
     ]
 }
\ No newline at end of file

Train/Track.svg

@@ -7,6 +7,12 @@
    version="1.1"
    id="svg5154">
 
+  <polygon id = "train_polygon"
+       points="0,0 100,0"
+       style="stroke-width: 0.3"
+       stroke="black" fill="lightgray"
+       transform="translate(10,16.8)" />
+       
   <polygon id = "track_polyline"
        points="0,0 1,0, 1,1 1,0 50,0 50,1 50,0 100,0"
        style="stroke-width: 0.3"