/* 

  Nrev benchmark in Picat.

  http://www.jekejeke.ch/idatab/doclet/prod/en/docs/05_run/15_stdy/06_bench/09_programs/01_nrev/01_nrev.p.html

  This Picat model was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/


% import util.
% import cp.


main => time(go).


/**
 * Prolog code for the naïve reverse benchmark.
 *
 * This is the benchmark of page 219 of:
 * Warren, D.H.D. (1983): Applied Logic – Its Use and
 * Implementation as a Programming Tool,
 * Technical Note 290, SRI International, 1983
 *
 */

% Prolog code
/*
rev([],[]).
rev([X|Rest],Ans) :- rev(Rest,L), concatenate(L,[X],Ans).

concatenate([],L,L).
concatenate([X|L1],L2,[X|L3]) :- concatenate(L1,L2,L3).

datanrev([1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,
                     21,22,23,24,25,26,27,28,29,30]).

nrev :- datanrev(X), rev(X,_).
*/


rev([],Y) => Y = [].
rev([X|Rest],Ans) => rev(Rest,L), concatenate(L,[X],Ans).

concatenate([],L,L2) => L2 = L.
concatenate([X|L1],L2,LL) => LL = [X|L3], concatenate(L1,L2,L3).

datanrev(D) => D = [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,
                     21,22,23,24,25,26,27,28,29,30].

% go => datanrev(X), rev(X,_).
go => datanrev(X), rev(X,Y), writeln(Y).

go2 => datanrev(X), rev(X,_Y).