Using the subgoal_abstract(Size) attribute, a tabled
subgoal that that is too large is abstracted by replacing
compound subterms of the goal with variables. In a nutshell, a goal
p(s(s(s(s(s(0)))))) is converted into the semantically
equivalent subgoal if the subgoal size is limited to 3.
...,
p(s(s(s(X)))), X = s(s(0)),
...,
As a result of this, terms stored in the variant trie that
maps goal variants into answer tables is limited. Note that
does not limit the number of answer tables as atomic values are never
abstracted and there are, for example, an infinite number of integers.
Note that restraining the subgoal size does not affect the semantics,
provided more general queries on the predicate include all answers that
more specific queries do. See also call substitution as
described in section
7.5. In addition to the tripwire actions, the max_table_subgoal_size_action
can be set to the value abstract:
- abstract
- Abstract the goal as described above and provide correctness by adding
the required unification instructions after the goal.
