It's possible this is something I never knew about: is it actually
correct that _all_ convenience variables are deleted when `file' is
used? The explanation above about their types being lost doesn't make
sense to me; can you explain? For example, if I define a variable
that holds an integer number, why would its type become meaningless?
Does this description assume that convenience variables point, or are
somehow related, to the symbol table? If so, why does this assumption
hold for every convenience variable? I can think of a convenience
variable that has no relation whatsoever to the symbol table; how does
such a variable fit into the above scheme?