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PL_new_atom()
Availability:C-language interface function
atom_t PL_new_atom(const char *)
Return an atom handle for the given C-string. This function always succeeds. The returned handle is valid as long as the atom is referenced (see section 12.4.2.1). Currently aborts the process with a fatal error on failure. Future versions may raise a resource exception and return (atom_t)0.

The following atoms are provided as macros, giving access to the empty list symbol and the name of the list constructor. Prior to version 7, ATOM_nil is the same as PL_new_atom("[]") and ATOM_dot is the same as PL_new_atom("."). This is no longer the case in SWI-Prolog version 7.

atom_t ATOM_nil(A)
tomic constant that represents the empty list. It is advised to use PL_get_nil(), PL_put_nil() or PL_unify_nil() where applicable.
atom_t ATOM_dot(A)
tomic constant that represents the name of the list constructor. The list constructor itself is created using PL_new_functor(ATOM_dot,2). It is advised to use PL_get_list(), PL_put_list() or PL_unify_list() where applicable.
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LogicalCaptain said (2021-04-18T10:04:32):0 upvotes 0 0 downvotes
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Something went wrong in formatting:

atom_t ATOM_nil(A) tomic constant that represents...

should be

atom_t ATOM_nil Atomic constant that represents...

There is also some problem with saying that ATOM_dot is the "list constructor" as "dot" is now the SWI-Prolog dict dereferencing operation, and the list constructor is `[|]` (sic).

Also:

"The returned handle is valid as long as the atom is referenced..." should be "The returned handle is valid as long as the atom's reference count is > 0". After call, the reference count is 1.

From PL_register_atom: "Increment the reference count of the atom by one. PL_new_atom performs this automatically, returning an atom with a reference count of at least one."