1/*  Part of Extended Libraries for Prolog
    2
    3    Author:        Edison Mera
    4    E-mail:        efmera@gmail.com
    5    WWW:           https://github.com/edisonm/xlibrary
    6    Copyright (C): 2015, Process Design Center, Breda, The Netherlands.
    7    All rights reserved.
    8
    9    Redistribution and use in source and binary forms, with or without
   10    modification, are permitted provided that the following conditions
   11    are met:
   12
   13    1. Redistributions of source code must retain the above copyright
   14       notice, this list of conditions and the following disclaimer.
   15
   16    2. Redistributions in binary form must reproduce the above copyright
   17       notice, this list of conditions and the following disclaimer in
   18       the documentation and/or other materials provided with the
   19       distribution.
   20
   21    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
   22    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
   23    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
   24    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
   25    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
   26    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
   27    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
   28    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
   29    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
   30    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
   31    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
   32    POSSIBILITY OF SUCH DAMAGE.
   33*/
   34
   35:- module(termhide, [op(1150, fx, hide)]).   36
   37:- use_module(library(sequence_list)).   38:- use_module(library(occurs)).   39:- reexport(library(compound_expand)).   40:- init_expansors.   41
   42/* <module> Term hide
   43
   44Inspired in the declaration ```:- hide Spec``` as described in the paper:
   45
   46N. Stulova, J. F. Morales, M. V. Hermenegildo. Towards Run-time Checks
   47Simplification via Term Hiding. Technical Communications of the 33rd
   48International Conference on Logic Programming (ICLP 2017), OpenAccess Series in
   49Informatics (OASIcs), Vol. 58, pages 91-93, Schloss Dagstuhl-Leibniz-Zentrum
   50fuer Informatik, 2017. (Extended Abstract).
   51
   52But note that the motivation to implement this is different than the one in such
   53paper.  What we want is to avoid irrestricted access to data structures out of a
   54given module.
   55*/
   56
   57:- multifile '$termhide'/2.   58
   59term_expansion_decl(hide(PIS), ClauseL) :-
   60    prolog_load_context(module, M),
   61    sequence_list(PIS, List, []),
   62    findall(termhide:'$termhide'(H, M),
   63            ( member(F/A, List),
   64              functor(H, F, A)
   65            ), ClauseL).
   66
   67scan(Scope, Goal) :-
   68    prolog_load_context(module, C),
   69    ( Scope = goal,
   70      predicate_property(C:Goal, meta_predicate(Meta))
   71    ->strip_module(C:Goal, I, Head),
   72      arg(N, Meta, Spec),
   73      \+ ( integer(Spec),
   74           Spec >= 0
   75         ),
   76      arg(N, Head, Term),
   77      ( Spec = (:)
   78      ->strip_module(I:Term, M, Arg)
   79      ; M = I,
   80        Head = Arg
   81      )
   82    ; strip_module(C:Goal, M, Arg)
   83    ),
   84    sub_term(Sub, Arg),
   85    nonvar(Sub),
   86    '$termhide'(Sub, T),
   87    M \= T,
   88    print_message(error, format("Explicit usage of hidden term ~w not allowed", [T:Sub])).
   89
   90term_expansion((:- Decl), Clauses) :-
   91    !,
   92    term_expansion_decl(Decl, Clauses).
   93% Next line reexports this module in cascade, to prevent usage of the term
   94% beyond a second level dependency:
   95term_expansion(end_of_file, [(:- reexport(library(termhide))), end_of_file]) :-
   96    \+ prolog_load_context(module, termhide),
   97    !.
   98term_expansion(Head :- _, _) :-
   99    !,
  100    scan(term, Head),
  101    fail.
  102term_expansion(Head --> _, _) :-
  103    !,
  104    scan(term, Head),
  105    fail.
  106term_expansion(Head, _) :-
  107    scan(term, Head),
  108    fail.
  109
  110goal_expansion(Goal, _) :-
  111    scan(goal, Goal),
  112    fail