/ GENTLE PRIMER
/ A Summary of Predefined Predicates
The Predicate where
The predicate where is defined for each type.
It simply copies its input parameter to its output parameter.
Hence, it may be used to construct a value and assign it to a variable
where(list(red, nil) -> L)
or to inspect a value and define variables with subterms as in
where(L -> list(Head, Tail))
This predicate is of particular use in alternative statements
and is discussed in the corresponding section.