[R] Portected? Variable assignment? Was RE: The use of F for False and T for True

[Lucke, Joseph F]

The TRUE/FALSE vs. T/F issue brings up a related one.  Can one assign a
variable a value during an R session that cannot be re-assigned any new
value during the session?  That is, the variable is `protected' from
change during the session.  `Session' here is not  precisely defined, so
that will induce some problems.  A reference to this problem would be
sufficient.