Tabling¶

YAPTab* is the tabling engine that extends YAP's execution model to support tabled evaluation for definite programs.

YAPTab was implemented by Ricardo Rocha and its implementation is largely based on the ground-breaking design of the XSB Prolog system, which implements the SLG-WAM. Tables are implemented using tries and YAPTab supports the dynamic intermixing of batched scheduling and local scheduling at the subgoal level. Currently, the following restrictions are of note:

• YAPTab does not handle tabled predicates with loops through negation (undefined behaviour).

• YAPTab does not handle tabled predicates with cuts (undefined behaviour).

• YAPTab does not support coroutining (configure error).

• YAPTab does not support tabling dynamic predicates (permission error).

To experiment with YAPTab use --enable-tabling in the configure script or add -DTABLING to YAP_EXTRAS in the system's Makefile. We next describe the set of built-ins predicates designed to interact with YAPTab and control tabled execution:

• tabling_statistics/0/0
• tabling_mode/3
• table_statistics/1
• table/1
• show_table/1
• is_tabled/1
• abolish_table/1