next up previous
Contents Next: nthcdr (FUNCTION) Up: Appendix: Selected Lisp Previous: not (PREDICATE)


Format: (nth <index> <list> )

Required arguments: 2

<index> : any expression which returns a positive integer (fixnum). <list> : any expression which returns a list.

The function nth returns the indexed element of <list> . <index> must be a non-negative integer. 0 indicates the first element of <list> , 1 the second, etc. An index past the end of the list will cause nth to return nil.


> (nth 0 '(picard riker work crusher))

> (nth 2 '((captain picard) 
          (commander riker) 
          (lieutenant worf)  
          (ensign crusher)))

© Colin Allen & Maneesh Dhagat
March 2007