changing list of strings to atoms using maplist?

1
votes

How to change string to atoms using maplist.

This does not work :

 ?- maplist(atom_string,["a","b","c"]).

first because atom_string/2 has arity of two (How do you do partial-function//currying in prolog).

But even if partial-fun worked the complication is that the first argument of atom_string is the unknown i.e. the call is :

  atom_string(A,"atom")

not :

  atom_string("atom",A)

this worked :

?- use_module(library(lambda)).

?- F = \Y^X^(atom_string(X,Y)), maplist(F,["a","b","c"],L).
F = \Y^X^atom_string(X, Y),
L = [a, b, c].
2
prologswi-prologpartial-applicationmaplist
correct ... i asked for changing "strings" to "atoms" using maplist, not "string" to "atom" ... changed the header to be more clear – sten
Why do you think atom_string(A, "atom") is a problem? SWI-Prolog's documentation for atom_string/2 says that it's bidirectional, and running the query ?- atom_string(A, "atom"). I get the expected answer A = atom.. – Isabelle Newbie

2 Answers

2
votes

This works as intended:

?- maplist(atom_string, Atoms, ["a","b","c"]).
Atoms = [a, b, c].

If this is not what you are after, please explain.

1
votes

Use a helper predicate.

string_atom(String,Atom) :-
    atom_string(Atom,String).

Then run using

?- maplist(string_atom,["a","b","c"],Atoms).
Atoms = [a, b, c].