HELP ATOM                                     Steven Hardy, January 1978
                                        Updated R. Barrett, January 1986

    atom(<item>) -> <boolean>

This procedure returns <false> if applied to a *PAIR, that is an object
to which the procedures *FRONT and *BACK can be applied.  Otherwise it
returns <true>.

Examples:

    atom([]) =>
    ** <true>

    atom("x") =>
    ** <true>

    atom([a b c d]) =>
    ** <false>

ATOM could be defined as:

    define atom(x);
       not(ispair(x))
    enddefine;

Attempting to apply HD or TL to an ATOM results in a MISHAP.  Note that
[], the empty list, is an ATOM.

See also HELP * NULL, * CONSPAIR, * FRONT, * BACK, * DESTPAIR, * HD, * TL.

For technical details see REF * LISTS