Arrays of entities

You're forgetting to tell the function to return an actor. By default, functions return an integer, so if you don't specify otherwise ($,#,%, or .YourTypeName) it'll return an integer.

Type actor
  Field x
  Field y
  Field z
End Type

Dim actors.actor(10)

For n=0 to 9
  actors.actor(n)=test_func()
next

Function test_func.actor()
  entity.actor=New actor
  entity\x = rnd(-10,10)
  entity\y = rnd(-10,10)
  entity\z = rnd(-10,10)
  Return entity
End Function