/* 

  Leonardo numbers (Rosetta code) in Picat.

  http://rosettacode.org/wiki/Leonardo_numbers
  """
  Leonardo numbers   are also known as the   Leonardo series.

  The   Leonardo numbers   are a sequence of numbers defined by:

       L(0) = 1                                          [1st equation]  
       L(1) = 1                                          [2nd equation]  
       L(n) = L(n-1)  +    L(n-2)   +  1                 [3rd equation]  
                    ─── also ───
       L(n) =      2  *  Fib(n+1)   -  1                 [4th equation]  

                  where the   + 1   will herein be known as the   add   number.
                  where the   FIB   is the   Fibonacci numbers.


   This task will be using the 3rd equation (above) to calculate the Leonardo numbers.

   Edsger W. Dijkstra   used   Leonardo numbers   as an integral part of his   smoothsort   algorithm.


   The first few Leonardo numbers are:

    1   1   3   5   9   15   25   41   67   109   177   287   465   753   1219   1973   3193   5167   8361  ··· 


   Task

   - show the 1st   25   Leonardo numbers, starting at L(0).
   - allow the first two Leonardo numbers to be specified   [for L(0) and L(1)].
   - allow the add number to be specified   (1 is the default).
   - show the 1st 25 Leonardo numbers, specifying 0 and 1 for L(0) and L(1), 
     and 0 for the add number.

   (The last task requirement will produce the Fibonacci numbers.)


    Show all output here on this page.
  """


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

*/

main => go.

go =>
  println([leonardo(I) : I in 0..24]),    
  println([leonardo(0,1,0,I) : I in 0..24]).

leonardo(N) = leonardo(1,1,1,N).
table
leonardo(I1,_I2,_Add,0) = I1.
leonardo(_I1,I2,_Add,1) = I2.
leonardo(I1,I2,Add,N) = leonardo(I1,I2,Add,N-1) + leonardo(I1,I2,Add,N-2) + Add.