The transformation of operators which contain `sg` definitions is shown
in the following example, a definition of Fibonacci numbers working on
both ordinary integers and their successor representation.

Applying `undeclare` to this operator transforms each `sg`
definition into an ordinary (`ft`) clause which calls an
operator `fib.`*n*
( ). The definitions
of `fib.`*n* are obtained simply by renaming the original
`fib` clauses, using `fib.1` for the first `sg`-block,
`fib.2` for the second, and `fib.3` for the third.