Functions

Named Functions

You define functions using the defun macro:

(defun fib (n) "Return the nth Fibonacci number." (if (< n 2) n (+ (fib (- n 1)) (fib (- n 2))))) 

And call them like you call anything else:

CL-USER> (fib 30) 832040 

Anonymous Functions

Application

Functions can be called indirectly using funcall:

CL-USER> (funcall #'fib 30) 832040 

Or with apply:

CL-USER> (apply #'fib (list 30)) 832040 

Multiple Return Values

(defun many (n) (values n (* n 2) (* n 3))) 

CL-USER> (multiple-value-list (many 2)) (2 4 6) CL-USER> (nth-value 1 (many 2)) 4 

We can also use multiple-value-bind to assign each return value to a variable:

CL-USER> (multiple-value-bind (first second third) (many 2) (list first second third)) (2 4 6)