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How to remove routines in the prolog?

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

"Given a list of integers. Remove all sub-lists formed from reduction elements."

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4 answers

We remove downstream signatures in three steps:

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

  • exclude non-single lists (using tfilter/3, prolog and lambdas(=)/3 )

    ?- tfilter(\[_|T]^(T=[]),[[1],[2],[3],[4,3,2,1],[2],[3],[4,3,2,1],[2]],Xs2).
Xs2 =                    [[1],[2],[3],          [2],[3],          [2]].

  • map lists of single elements to elements (using maplist/3and Prolog lambdas )

    ?- maplist(\[H|_]^H^true,[[1],[2],[3],[2],[3],[2]],Xs).
Xs =                     [ 1 , 2 , 3 , 2 , 3 , 2 ].

Let it all be together!

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

descending_removed(Xs0,Xs) :-
   splitlistIfAdj(#=<,Xs0,Xs1),
   tfilter(\[_|T]^(T=[]),Xs1,Xs2),
   maplist(\[H|_]^H^true,Xs2,Xs).

Here are a few queries:

?- 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].
+3

, tchoose/3 tfilter/3 maplist/3, - :

  • ( splitlistIfAdj/3 (#=<)/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]].

  • ( tchoose/3, Prolog lambdas (=)/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 ].

!

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

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

, :

?- 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].
+3

:

1 2 3 4 3 2 1 2 3 4 3 2 1 2


1 2 3 2 3 2

? , "" :

A B C
  1 2   -> output 1
1 2 3   -> output 2
2 3 4   -> output 3
3 4 3   -> output none
4 3 2   -> output none
3 2 1   -> output none
2 1 2   -> output none
1 2 3   -> output 2
2 3 4   -> output 3
3 4 3   -> output none
4 3 2   -> output none
3 2 1   -> output none
2 1 2   -> output none
1 2     -> output 2

, B , A < B < C. : . , B.

remove_dec([], []).
remove_dec(Input, Output) :-
    min_list(Input, Min),
    remove_dec0([ Min | Input ], Output).
remove_dec0([ A, B, C | Input], [ B | Output ]) :-
    A =< B, B =< C,
    remove_dec0([ B, C | Input], Output).
remove_dec0([ _, B, C | Input], Output) :-
    remove_dec0([ B, C | Input], Output).
remove_dec0([A, B], [B]) :-
    A =< B.
remove_dec0([A, B], []) :-
    A > B.

:

?- remove_dec([1,2,3,4,3,2,1,2,3,4,3,2,1,2],R).
R = [1, 2, 3, 2, 3, 2] .

?- remove_dec([4,3,2,1,0],R).
R = [] ;
false.

?- remove_dec([1,2,3,4],R).
R = [1, 2, 3, 4] .
+2

( , ):

descending_removed(L,R) :- dr(a,L,R).

dr(_,[],[]).

dr(DIR,[A|Q],R) :-
  ( [B|_]=Q, A>B ->  
        dr(d,Q,R)
  ;
        dr(a,Q,T), ( DIR=a -> R=[A|T]; R=T )
  ).

:

test :-
  descending_removed([1,2,3,4,3,2,1,2,3,4,3,2,1,2],[1,2,3,2,3,2]),
  descending_removed([4,3,2,1,0],[]),
  descending_removed([1,2,3,4],[1,2,3,4]),
  descending_removed([1,2,3,4,3,3,2,2,1],[1,2,3]),
  descending_removed([1,2,3,4,4,3,3,2,2,1],[1,2,3,4]),
  descending_removed([1],[1]).

:

[debug]  ?- test.
true ;
false.

, , :

descending_removed(L,R) :- dr(a,L,R).

dr(_,[],[]).

dr(DIR,[A|Q],R) :-
  ( [B|_]=Q, A>B ->  
        dr(d,Q,R)
  ; [B|_]=Q, A=B ->  
        dr(DIR,Q,T), ( DIR=a -> R=[A|T]; R=T )   
  ;   
        dr(a,Q,T), ( DIR=a -> R=[A|T]; R=T )
  ).

:

descending_removed([1,2,2,2,3,4,3,3,2,2,1],R).
R = [1, 2, 2, 2, 3] ;
false

descending_removed([1,2,3,3,2,4,3,3,2,2,5],R).
R = [1, 2, 3, 5]
false
+1

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