Question

I try to build predicate which will append random number of sublists result list.

my_predicate([], AnotherList, []).
my_predicate([Head|List], AnotherList, Result):-
  random(0,5,N),
  nested_predicate(N, Head, AnotherList, SM),
  my_predicate(List, AnotherList, Result),
  append(SM, Result, SM2),
  write(SM2).

And everything nearly ok, but I cannot assign SM2 to Result in any way. What I’m doing so wrong?

Answer 1

In Prolog, you cannot “assign” a value to a variable. Also, in your code, Result will always be bound to an empty list.

I assume what you want is something like this:

my_predicate([], AnotherList, []).
my_predicate([Head|List], AnotherList, Result):-
  random(0,5,N),
  nested_predicate(N, Head, AnotherList, SM),
  my_predicate(List, AnotherList, SM2),
  append(SM, SM2, Result),
  write(Result).