Jan Burse, erstellt 21. Okt 2018
* When a goal belonging to a defined predicate is invoked a new frame
* is created. When the interpreter encounters a cut (!) it will remove
* the choice points inside the frame. To instruct the interpreter that
* cuts can nevertheless propagate a defined predicate can be marked as
* cut transparent via the predicate property sys_nobarrier/1.
* ?- X = a; X = b.
* X = a ;
* X = b
* ?- X = a, !; X = b.
* X = a
* Some of the predefined logical predicates are cut transparent in all
* arguments. This includes the predicates (,)/2 and (;)/2. Others are
* only cut transparent in a few arguments. This includes the predicates
* (->)/2 and (*->)/2, and also the special forms in connection with the
* predicate (;)/2. Others are not cut transparent at all. This includes
* the predicates sys_call/1, call/1, once/1 and (\+)/1.
* Warranty & Liability
* To the extent permitted by applicable law and unless explicitly
* otherwise agreed upon, XLOG Technologies GmbH makes no warranties
* regarding the provided information. XLOG Technologies GmbH assumes
* no liability that any problems might be solved with the information
* provided by XLOG Technologies GmbH.
* Rights & License
* All industrial property rights regarding the information - copyright
* and patent rights in particular - are the sole property of XLOG
* Technologies GmbH. If the company was not the originator of some
* excerpts, XLOG Technologies GmbH has at least obtained the right to
* reproduce, change and translate the information.
* Reproduction is restricted to the whole unaltered document. Reproduction
* of the information is only allowed for non-commercial uses. Selling,
* giving away or letting of the execution of the library is prohibited.
* The library can be distributed as part of your applications and libraries
* for execution provided this comment remains unchanged.
* Only to be distributed with programs that add significant and primary
* functionality to the library. Not to be distributed with additional
* software intended to replace any components of the library.
* Jekejeke is a registered trademark of XLOG Technologies GmbH.
* A; B: [ISO 7.8.6]
* The predicate succeeds whenever A or B succeeds. Both goal
* arguments A and B are cut transparent.
* A -> B;C: [ISO 7.8.8]
* The predicate succeeds when A succeeds and then whenever B succeeds, or
* else whenever C succeeds. Only the goal arguments B and C are
* cut transparent.
* A *-> B; C:
* The predicate succeeds whenever A and B succeed, or else if B didn’t
* succeed whenever C succeeds. Only the goal arguments B and C are
* cut transparent.
% +Goal ; +Goal
% sys_cond(+Goal, +Goal, +Goal)
% sys_soft_cond(+Goal, +Goal, +Goal)
* The predicate marks the choice point of the direct parent, if there is any
* at all, as non-redo able and then succeeds once.
sys_soft_local_cut/0, 'SpecialLogic', 1).
* A -> B: [ISO 7.8.7]
* The predicate succeeds when A succeeds and then whenever B
* succeeds. Only the goal argument B is cut transparent.
% +Goal -> +Goal
* The predicate removes pending choice points between the direct parent
* goal invocation and this goal and then succeeds once.
sys_local_cut/0, 'SpecialLogic', 0).
* A *-> B:
* The predicate succeeds whenever A and B succeed. Only the goal
* argument B is cut transparent.
% +Goal *-> +Goal
* The predicate succeeds whenever A succeeds. The goal
* argument A is not converted before calling.
* repeat: [ISO 8.15.3]
* The predicate succeeds repeatedly.