Useful Common Lisp Functions

Predicates

• LISTP - returns t if argument is a list
• ATOM - returns t if arg is an atom, nil otherwise
• NULL - returns t if argument is the null list
• EQ - returns t if two arguments are identical.
• EQUAL - returns t if two arguments have same elements
• MINUSP - returns t if arg is a negative number
• PLUSP - returns t if arg is a positive number
• NUMBERP - returns t if arg is a number
• ZEROP - returns t if arg is the number 0

Logic functions

• AND - evaluates arguments in turn, until one returns false or last argument is reached. returns value of last argument evaluated
• OR - evaluates arguments in turn, until one returns true or last argument is reached. Returns value of last argument evaluated
• NOT - returns t if arg is nil, otherwise nil.

List functions

• CAR - returns the head of a list
• CDR - returns the tail of the list
• CONS - add an element to a list, eg (cons '(a b) '(c d)) = ((a b) c d)
• APPEND - joins to lists, eg (append '(a b) '(c d)) = (a b c d).
• MEMBER - returns the list that begins with the first argument, eg (member 'a  '(b c a d)) returns (a d)
• CADR - returns the car of the cdr of a list (ie the second element)
• CADDR - returns the car of the cdr of the cdr of a list (ie the third element)
• REVERSE - (reverse '(a (b c) d)) = (d (b c) a)

Defining functions

• DEFUN - (defun somefun(a b) ( ... )) defines a function somefun that has two arguments
• EVAL - evaluates its argument

Numeric functions

• MAX - maximum in the list
• MIN - minimum in the list
• ABS - absolute value
• SQRT - square root
• +, -, *, /,>,>=, ...

Others

• (BYE)
• LOAD - (LOAD "fn.lsp")
• HELP - (help 'car)
  
• TRACE - (trace aaa bbb) Causes all calls to aaa and bbb to be traced
• PRIN1 - prints its argument, without a newline.
• PRINT - prints its argument and then a newline.
• READ - reads and returns an S-expression.