Remove SwapFirstEntityGroup, it may have created misunderstanding and it's not strictly needed.

Svelto.ECS/EnginesRoot.Entities.cs

@@ -200,13 +200,6 @@ namespace Svelto.ECS
             MoveEntity(builders, new EGID(entityID, fromGroupID), toGroupID, toGroup);
         }
         
-        void SwapFirstEntityInGroup(IEntityBuilder[] builders, int fromGroupID, int toGroupId)
-        {
-            var firstID = _groupEntityDB[fromGroupID][builders[0].GetEntityType()].GetFirstID();
-            
-            SwapEntityGroup(builders, firstID, fromGroupID, toGroupId);
-        }
-
         readonly EntitiesDB         _DB;
         int                         _newEntitiesBuiltToProcess;
     }

Svelto.ECS/EnginesRoot.GenericEntityFunctions.cs

@@ -69,18 +69,6 @@ namespace Svelto.ECS
                 _weakReference.Target.QueueEntitySubmitOperation(
                     new EntitySubmitOperation(EntitySubmitOperationType.Swap, id.entityID, id.groupID, (int)toGroupID, EntityDescriptorTemplate<T>.descriptor.entitiesToBuild));
             }
-            
-            public void SwapFirstEntityGroup<T>(int fromGroupID, int toGroupID) where T : IEntityDescriptor, new()
-            {
-                _weakReference.Target.QueueEntitySubmitOperation(
-                    new EntitySubmitOperation(EntitySubmitOperationType.FirstSwap, -1, fromGroupID, toGroupID, EntityDescriptorTemplate<T>.descriptor.entitiesToBuild));
-            }
-
-            public void SwapFirstEntityGroup<T>(ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new()
-            {
-                _weakReference.Target.QueueEntitySubmitOperation(
-                    new EntitySubmitOperation(EntitySubmitOperationType.FirstSwap, -1, (int)fromGroupID, (int)toGroupID, EntityDescriptorTemplate<T>.descriptor.entitiesToBuild));
-            }
         }
 
         void QueueEntitySubmitOperation(EntitySubmitOperation entitySubmitOperation)

Svelto.ECS/EnginesRoot.Submission.cs

@@ -27,9 +27,6 @@ namespace Svelto.ECS
                     case EntitySubmitOperationType.Remove:
                         MoveEntity(entitiesOperations[i].builders, new EGID(entitiesOperations[i].id, entitiesOperations[i].fromGroupID));
                         break;
-                    case EntitySubmitOperationType.FirstSwap:
-                        SwapFirstEntityInGroup(entitiesOperations[i].builders, entitiesOperations[i].fromGroupID, entitiesOperations[i].toGroupID);
-                        break;
                     case EntitySubmitOperationType.RemoveGroup:
                         RemoveGroupAndEntitiesFromDB(entitiesOperations[i].fromGroupID);
                         break;

Svelto.ECS/EntitySubmitOperation.cs

@@ -22,7 +22,6 @@
     {
         Swap,
         Remove,
-        FirstSwap,
         RemoveGroup
     }
 }

Svelto.ECS/IEntityFunctions.cs

@@ -5,7 +5,7 @@ namespace Svelto.ECS
     public interface IEntityFunctions
     {
         //being entity ID globally not unique, the group must be specified when
-        //an entity is removed. Not specificing the group will attempt to remove
+        //an entity is removed. Not specifying the group will attempt to remove
         //the entity from the special standard group.
         void RemoveEntity<T>(int entityID, int groupID) where T : IEntityDescriptor, new();
         void RemoveEntity<T>(int entityID, ExclusiveGroup groupID) where T : IEntityDescriptor, new();
@@ -18,7 +18,5 @@ namespace Svelto.ECS
         void SwapEntityGroup<T>(int entityID, ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new();
         void SwapEntityGroup<T>(EGID id, int toGroupID) where T : IEntityDescriptor, new();
         void SwapEntityGroup<T>(EGID id, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new();
-        void SwapFirstEntityGroup<T>(int fromGroupID, int toGroupID) where T : IEntityDescriptor, new();
-        void SwapFirstEntityGroup<T>(ExclusiveGroup fromGroupID, ExclusiveGroup toGroupID) where T : IEntityDescriptor, new();
     }
 }