/**
         
 * Modern Albufeira Prolog Interpreter
         
 *
         
 * Warranty & Liability
         
 * To the extent permitted by applicable law and unless explicitly
         
 * otherwise agreed upon, XLOG Technologies AG makes no warranties
         
 * regarding the provided information. XLOG Technologies AG assumes
         
 * no liability that any problems might be solved with the information
         
 * provided by XLOG Technologies AG.
         
 *
         
 * Rights & License
         
 * All industrial property rights regarding the information - copyright
         
 * and patent rights in particular - are the sole property of XLOG
         
 * Technologies AG. If the company was not the originator of some
         
 * excerpts, XLOG Technologies AG 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.
         
 *
         
 * Restrictions
         
 * 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.
         
 *
         
 * Trademarks
         
 * Jekejeke is a registered trademark of XLOG Technologies AG.
         
 */
         

         
:-(offset(C, Goal), ','(sys_call_nth(Goal, N), >(N, C))).
         
:-(limit(C, Goal), ','(>(C, 0), ','(sys_call_nth(Goal, N), ;(->(<(N, C), true), !)))).
         
:-(call_nth(Goal, C), ','(var(C), ','(!, ','(sys_call_nth(Goal, N), =(C, N))))).
         
:-(call_nth(Goal, C), ','(>(C, 0), ','(sys_call_nth(Goal, N), ;(->(=:=(C, N), !), fail)))).
         
:-(sys_call_nth(Goal, N), ','(=(Holder, v(_)), ','(change_arg(1, Holder, 0), ','(Goal, ','(arg(1, Holder, M), ','(is(N, +(M, 1)), change_arg(1, Holder, N))))))).
         
:-(distinct(Goal), ','(term_variables(Goal, W), ','(findall(W, Goal, L), ','(list_to_set(L, R), member(W, R))))).