Prolog - Add a special character to every element of a list-CodePudding

I'm trying to add a special character (*) to every element of a list.

I want to add it in the beginning and the end of the element, so if I have:

list(apple,orange,pear)

It would be:

list(*apple*,*orange*,*pear*)

Is there a way to do that in prolog?

Thank you.

CodePudding user response：

To concatenate two atoms, you can use the ISO predicate atom_concat/3:

?- atom_concat('*', apple, StarAtom), atom_concat(StarAtom, '*', StarAtomStar).
StarAtom = '*apple',
StarAtomStar = '*apple*'.

Using this predicate, you can define the following new predicate:

% starry_atom( Atom, -StarAtomStar)

  starry_atom(Atom, StarAtomStar) :-
      atom_concat('*', Atom, StarAtom),
      atom_concat(StarAtom, '*', StarAtomStar).

Example:

?- starry_atom(apple, StarryAtom).
StarryAtom = '*apple*'.

To apply starry_atom/2 to all elements of a list, supposing that all elements of the list are atoms, you can use the predicate maplist/3.

?- maplist(starry_atom, [apple, orange, pear], List).
List = ['*apple*', '*orange*', '*pear*'].

NOTE In SWI-Prolog, you can also use the predicate atomic_list_concat/2.

?- atomic_list_concat(['*', apple, '*'], Atom).
Atom = '*apple*'.