allow Physicals as right values in FExprs

Parser/Gmsh.y

@@ -4219,6 +4219,78 @@ FExpr_Multi :
     {
       $$ = GetAllEntityNumbers(3);
     }
+  | tPhysical tPoint '{' RecursiveListOfDouble '}'
+    {
+      $$ = List_Create(10, 1, sizeof(double));
+      for(int i = 0; i < List_Nbr($4); i++){
+        double num;
+        List_Read($4, i, &num);
+        PhysicalGroup *p = FindPhysicalGroup((int)num, MSH_PHYSICAL_POINT);
+        if(p){
+          for(int j = 0; j < List_Nbr(p->Entities); j++){
+            int nume;
+            List_Read(p->Entities, j, &nume);
+            double d = nume;
+            List_Add($$, &d);
+          }
+        }
+      }
+      List_Delete($4);
+    }
+  | tPhysical tLine '{' RecursiveListOfDouble '}'
+    {
+      $$ = List_Create(10, 1, sizeof(double));
+      for(int i = 0; i < List_Nbr($4); i++){
+        double num;
+        List_Read($4, i, &num);
+        PhysicalGroup *p = FindPhysicalGroup((int)num, MSH_PHYSICAL_LINE);
+        if(p){
+          for(int j = 0; j < List_Nbr(p->Entities); j++){
+            int nume;
+            List_Read(p->Entities, j, &nume);
+            double d = nume;
+            List_Add($$, &d);
+          }
+        }
+      }
+      List_Delete($4);
+    }
+  | tPhysical tSurface '{' RecursiveListOfDouble '}'
+    {
+      $$ = List_Create(10, 1, sizeof(double));
+      for(int i = 0; i < List_Nbr($4); i++){
+        double num;
+        List_Read($4, i, &num);
+        PhysicalGroup *p = FindPhysicalGroup((int)num, MSH_PHYSICAL_SURFACE);
+        if(p){
+          for(int j = 0; j < List_Nbr(p->Entities); j++){
+            int nume;
+            List_Read(p->Entities, j, &nume);
+            double d = nume;
+            List_Add($$, &d);
+          }
+        }
+      }
+      List_Delete($4);
+    }
+  | tPhysical tVolume '{' RecursiveListOfDouble '}'
+    {
+      $$ = List_Create(10, 1, sizeof(double));
+      for(int i = 0; i < List_Nbr($4); i++){
+        double num;
+        List_Read($4, i, &num);
+        PhysicalGroup *p = FindPhysicalGroup((int)num, MSH_PHYSICAL_VOLUME);
+        if(p){
+          for(int j = 0; j < List_Nbr(p->Entities); j++){
+            int nume;
+            List_Read(p->Entities, j, &nume);
+            double d = nume;
+            List_Add($$, &d);
+          }
+        }
+      }
+      List_Delete($4);
+    }
   | Transform
     {
       $$ = List_Create(List_Nbr($1), 1, sizeof(double));

doc/texinfo/gmsh.texi

@@ -1336,6 +1336,7 @@ List of expressions are also widely used, and are defined as:
   @var{extrude}
   Point @{ @var{expression} @} |
   Point|Line|Surface|Volume "*" |
+  Physical Point|Line|Surface|Volume @{ @var{expression-list} @}
 @c  @var{duplicata} - already implemented: should we explain this?
 @end example
 
@@ -1350,10 +1351,11 @@ permits to reference an expression sublist (whose elements are those
 corresponding to the indices provided by the @var{expression-list}).
 The next two cases permit to retrieve the indices of entities created
 through geometrical transformations and extrusions (see
-@ref{Transformations}, and @ref{Extrusions}). The last two cases permit
-to retrieve the coordinates of a given geometry point (@pxref{Points}),
-or to retrieve the id numbers of all points, lines, surfaces or volumes
-in the model.
+@ref{Transformations}, and @ref{Extrusions}). The last three cases
+permit to retrieve the coordinates of a given geometry point
+(@pxref{Points}), to retrieve the id numbers of all points, lines,
+surfaces or volumes in the model, or to retrieve the elementary entities
+making up physical groups.
 
 To see the practical use of such expressions, have a look at the first
 couple of examples in @ref{Tutorial}. Note that, in order to lighten the