LISP implementations typically have a large number of built-in functions. However, these functions are not standardized. Even some of the most fundamental operations may have different names, or vary somewhat in operation, from one implementation to the next. Hence, the following list of functions should be regarded as tentative.

In the following, A stands for an atom, L stands for a list, NEL stands for a nonempty list, N stands for a number, and S stands for an arbitrary S-expression.

Fundamental operations:

'S

(Special syntax) This is the same as (QUOTE S).

(LIST S1 S2 ...)

Form a list of the (evaluated) arguments S1, S2, ....

(CAAR NEL)

Same as (CAR (CAR NEL)). The first element of NEL must itself be a nonempty list; this function returns the first element in that nested list.

(CADR NEL)

Same as (CAR (CDR NEL)). Returns the second element of NEL (NEL must have at least two elements).

(CDAR NEL)

Same as (CDR (CAR NEL)). The first element of NEL must itself be a nonempty list.

(CDDR NEL)

Same as (CDR (CDR NEL)). Returns the result of removing the first two elements from the list NEL (NEL must have at least two elements).

Various LISPs define additional functions whose names consist of a C, some number of As and Ds, and an R, with the obvious meanings. Common LISP allows up to four As and Ds.

(SETQ A S)

Assign to the (unevaluated) atom A the value obtained by evaluating S. Hereafter, when A is evaluated, this is the value that will be returned.

Basic operations on lists:

(LIST S1 S2 ...)

Form a list of the (evaluated) arguments S1, S2, ....

(MEMBER S L)

Test whether S is a top-level (i.e. not embedded in a sublist) element of L.

(APPEND L1 L2 ...)

Make a new list from the elements of L1, L2, ..., in order.

(REVERSE L)

Return a list containing the same elements as L but in reverse order.

(LENGTH L)

Returns the length of L, that is, the number of top-level elements in L.

Predicates (tests):

(LISTP S)

True if S is a list.

(NUMBERP S)

True if S is a number.

(NOT S)

True if S is false, and false if S is true. Same as (NULL S).

(EQUAL S1 S2)

True if S1 and S2 are equal. Like EQ, but may be used for anything.

(ZEROP N)

True if number N is zero.

(PLUSP N)

True if number N is positive.

(MINUSP N)

True if number N is negative.

(EVENP N)

True if integer N is even.

(ODDP N)

True if integer N is odd.

Arithmetic operations:

(+ N1 N2 ...)

Returns the sum of the numbers.

(- N1 N2 ...)

Returns the result of subtracting all subsequent numbers from N1 .

(* N1 N2 ...)

Returns the product of all the numbers.

(/ N1 N2 ...)

Returns the result of dividing N1 by all subsequent numbers.

(1+ N)

Returns N plus one. (Note that there is no space between the "1" and the "+".)

(1- N)

Returns N minus one. (Note that there is no space between the "1" and the "-".)

(/ N)

Return the reciprocal of N.

Input/output:

(LOAD F)

Load the source file whose name (without extensions) is F .

(DRIBBLE F)

Causes the current session to be recorded file whose name (without extensions) is F . To stop recording, call (DRIBBLE) with no parameters. Not available on all systems.

(PRIN1 S)

Print, on the current line, the result of evaluating the S-expression S.

(TERPRI)

Print a newline.