/* 

  Euler #16 in Picat.

  Problem 16
  """
  2^15 = 32768 and the sum of its digits is 3 + 2 + 7 + 6 + 8 = 26.
  
  What is the sum of the digits of the number 2^1000?
  """

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

*/


main => time(go).

go => euler16.

% both these version are between 0s and 0.004s.

euler16 => 
  println(sum([I.to_integer() : I in (2**1000).to_string()])).

euler16b =>
  sum2((2**1000).to_string(), 0, Sum),
  println(Sum).

% recursive version
sum2([],Sum0,Sum) =>
  Sum = Sum0.

sum2([H|T],Sum0,Sum) => 
  Sum1 = H.to_integer()+Sum0,
  sum2(T,Sum1,Sum).