|II. Basic functions|
DEFUN is used to define new functions. It
takes three parameters, which are implicitly quoted (see below): (1) the name
of the function, as an atom; (2) the formal parameter list of the function,
as a list of atoms; and (3) an S-expression representing the body of the function.
DEFUN defines the new function and return as its value the name
of the function. (Note: some LISP systems use some other function, such as
to define functions.)
QUOTE takes a single S-expression
as a parameter, and returns that S-expression, unevaluated, as
CAR of a nonempty list is the
first element (S-expression) in that list.
CDR of a nonempty list is the
list with its first element removed.
CONS of an S-expression to a
list is the list with the S-expression inserted at the beginning, as a
new first element. Note that the
CAR of this new list is
the given S-expression, while the
CDR is the original
EQ compares two atoms for
equality (identity) and returns "true'' if the atoms are the same,
NIL if they are different.
ATOM of an S-expression is "true''
if the S-expression is an atom, and
NULL of an S-expression is "true''
if the S-expression is the empty list (that is,