/* 

  Return multiple values (Rosetta code) in Picat.

  http://rosettacode.org/wiki/Return_multiple_values
  """
  Show how to return more than one value from a function.
  """


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

*/

/*

  Functions returns a single value. Multiple values must be collected in a list (or an array, map, set, structure).


  Predicates
  Sometimes it is not possible - or not convenient - to create a function that return values.
  In those cases a predicate is used and some of the variables are considered output values
  and are usually placed as the last parameters.

  A variant of this is to use a structure (here $ret(A,B,C)) that collects the output values.

  (In some cases the name input/output values are muzzled when a predicate can be used
  with multiple input/output modes, e.g. reversible predicates such as append/3 or member/2.)


*/

main => go.

go =>
  [A,B,C] = fun(10),
  
  pred(10, E,F,G),
  
  println([E,F,G]),

  pred2(10, Ret),
  println(Ret),
  % or
  pred2(10,$ret(H,I,J)),
  println([H,I,J]),
  
  nl.



fun(N) = [2*N-1,2*N,2*N+1].

% A, B, and C are output values
pred(N, A,B,C) =>
  A=2*N-1,
  B=2*N,
  C=2*N+1.

% The structure $ret(A,B,C) is the output value.
pred2(N, ret(A,B,C)) :-
  A=2*N-1,
  B=2*N,
  C=2*N+1.