How to remove sub-lists in prolog?

Question

Can someone help me, please? I need to solve this problem in prolog and I don't know how...

"Given a list of integer numbers. Remove all sub-lists formed from decreases elements."

Answer 1

We can improve this answer by using tchoose/3 instead of tfilter/3 and maplist/3, removing descending sublists in two steps---not three:

1. separate decreasing and non-decreasing parts (using splitlistIfAdj/3 and (#=<)/3)

   ?- splitlistIfAdj(#=<,[ 1 , 2 , 3 , 4,3,2,1 , 2 , 3 , 4,3,2,1 , 2 ],Xs1).
   Xs1 =                 [[1],[2],[3],[4,3,2,1],[2],[3],[4,3,2,1],[2]].
   

2. filter singleton lists and map to items (using tchoose/3, Prolog lambdas, and (=)/3)

   ?- tchoose(\[H|T]^H^(T=[]),[[1],[2],[3],[4,3,2,1],[2],[3],[4,3,2,1],[2]],Xs).
   Xs =                       [ 1 , 2 , 3 ,           2 , 3 ,           2 ].
   

Let's put it together!

:- use_module(library(clpfd)).
:- use_module(library(lambda)).

descending_removed(Xs0,Xs) :-
   splitlistIfAdj(#=<,Xs0,Xs1),
   tchoose(\[H|T]^H^(T=[]),Xs1,Xs).

Same queries, same results:

?- descending_removed([1,2,3,4,3,2,1,2,3,4,3,2,1,2],Xs).
Xs = [1,2,3,2,3,2].

?- descending_removed([4,3,2,1,0],Xs).
Xs = [].

?- descending_removed([1,2,3,4],Xs).
Xs = [1,2,3,4].

?- descending_removed([1,2,3,  4,3,3,2,2,1],Xs).
Xs = [1,2,3].

?- descending_removed([1,2,3,4,4,3,3,2,2,1],Xs).
Xs = [1,2,3,4].