/* 

  Query benchmark in Picat.

  From
  http://www.jekejeke.ch/idatab/doclet/prod/en/docs/05_run/15_stdy/06_bench/09_programs/08_query/01_query.p.html

  Query population and area database to find countries
  of approximately equal population density.


  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 => go.



/**
 * Prolog code for the database query benchmark.
 *
 * This is the benchmark of page 226 of:
 * Warren, D.H.D. (1983): Applied Logic – Its Use and
 * Implementation as a Programming Tool,
 * Technical Note 290, SRI International, 1983
 *
 * We use integer division instead of float division,
 * Further complication by two temporary variables T1 and T2.
 *
 * Copyright 2010, XLOG Technologies GmbH, Switzerland
 * Jekejeke Prolog 0.8.3 (a fast and small prolog interpreter)
 */

index(-,-)
pop(china,        8250).
pop(india,        5863).
pop(ussr,         2521).
pop(usa,          2119).
pop(indonesia,    1276).
pop(japan,        1097).
pop(brazil,       1042).
pop(bangladesh,    750).
pop(pakistan,      682).
pop(w_germany,     620).
pop(nigeria,       613).
pop(mexico,        581).
pop(uk,            559).
pop(italy,         554).
pop(france,        525).
pop(philippines,   415).
pop(thailand,      410).
pop(turkey,        383).
pop(egypt,         364).
pop(spain,         352).
pop(poland,        337).
pop(s_korea,       335).
pop(iran,          320).
pop(ethiopia,      272).
pop(argentina,     251).

index(+,-)
area(china,       3380).
area(india,       1139).
area(ussr,        8708).
area(usa,         3609).
area(indonesia,    570).
area(japan,        148).
area(brazil,      3288).
area(bangladesh,    55).
area(pakistan,     311).
area(w_germany,     96).
area(nigeria,      373).
area(mexico,       764).
area(uk,            86).
area(italy,        116).
area(france,       213).
area(philippines,   90).
area(thailand,     200).
area(turkey,       296).
area(egypt,        386).
area(spain,        190).
area(poland,       121).
area(s_korea,       37).
area(iran,         628).
area(ethiopia,     350).
area(argentina,   1080).

density(C, D) =>
  pop(C, P),
  area(C, A),
  D = P*100 // A.

query =>
  density(C1, D1),
  density(C2, D2),
  D1 > D2,
  T1 = 20 * D1,
  T2 = 21 * D2,
  T1 < T2,
  writeln([T1,T2]),
  writeln([D1,D2]),
  writeln([C1,C2]).

go => query.