PPT Slide

For mapping functions of 2 ( or more ) arguments, mapcar requires 2 ( or more ) lists.

( mapcar # '+ '( 1 7 3 9 ) '( 8 6 2 3 ) )

returns ( 9 13 5 12 )

More examples

( defun twice ( n ) ( + n n ) )

( defun double ( L ) ( mapcar #'twice L ) )

( assoc < key > < association list > )

searches for and returns the first ( 2 element ) sublist whose car matches the key.

( setf words '( ( one un ) ( two deux ) ( three trois ) ) )

( defun trans-word ( w ) ( cadr ( assoc w words ) ) )

( defun trans-list ( L ) ( mapcar #'trans-word L ) )

( trans-list ' ( two three one two ) )