t.is_null()
is the same as t.unwrap() == PlTerm::null
t.not_null()
is the same as t.unwrap() !=
PlTerm::null
t.reset()
is the same as t.unwrap() = PlTerm::null
t.reset(x)
is the same as t.unwrap() = x
PL_VARIABLE
, PL_FLOAT
, PL_INTEGER
,
PL_ATOM
, PL_STRING
or PL_TERM
To avoid very confusing combinations of constructors and therefore
possible undesirable effects a number of subclasses of PlTerm
have been defined that provide constructors for creating special Prolog
terms. These subclasses are defined below.