1/*  Part of SWI-Prolog
    2
    3    Author:        Jan Wielemaker
    4    E-mail:        J.Wielemaker@vu.nl
    5    WWW:           http://www.swi-prolog.org
    6    Copyright (c)  2019, VU University Amsterdam
    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(setof,
   36          [ excess_vars/4	% +Term, +ExistVarTerm, +AddVarList, -VarList
   37          ]).   38:- use_module(library(lists)).   39
   40%!  excess_vars(+Term, +ExistVarTerm, +AddVarList, -VarList)
   41%
   42%   Returns in VarList the  list  of   (free)  variables  found  in Term
   43%   concatenated to the end of AddVarList.   (In normal usage AddVarList
   44%   is passed in as an empty list.)   ExistVarTerm  is a term containing
   45%   variables assumed to  be  quantified  in   Term  so  none  of  these
   46%   variables are returned in the  resulting   list  (unless they are in
   47%   AddVarList.) Subterms of Term of   the  form `(VarTerm^SubTerm)` are
   48%   treated specially: all variables  in  VarTerm   are  assumed  to  be
   49%   quantified in SubTerm, and so no   occurrence  of these variables in
   50%   SubTerm is collected into the resulting list.
   51
   52excess_vars(Term, ExistVarTerm, AddVarList, VarList) :-
   53    '$free_variable_set'(ExistVarTerm^Term, _Goal, Vars0),
   54    append(AddVarList, Vars0, VarList)