/* 

  Common utils in Picat.

  Utilities that are used both in ppl_utils.pi and ppl_distributions.


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

*/

module ppl_common_utils.

import util.


/*
  cumsum(L)
  Accumulative sum of L
*/
cumsum(L) = scanl1(+,L).
asum(L) = cumsum(L). % alias

scanl(_F, E, []) = [E].
scanl(F,E,Xs) = [E] ++ scanlT(F,E,Xs).
scanlT(_F,_A,[]) = [].
scanlT(F,A,[Y|Ys]) = scanl(F, apply(F,A,Y), Ys).

scanl1(_F,[]) = _ => throw $error(empty_list,scanl1,[]).
scanl1(F, [X|Xs]) = scanl(F,X,Xs).


/*
  differences(L)

  Returns the differences of L

*/
differences(L) = [L[I+1]-L[I] : I in 1..L.len-1].