| | 45 seconds | Name binding, Recursion, Iteration, and Continuations - slide 17 : 42 |
A list is a recursive data structure
As a consequence list processing is done via recursive functions
We illustrate list processing by extracting attribute values from a LAML attribute property list
; Return the href attribute value from a property list
; Return #f if no href attribute is found.
; Pre-condition: attr-p-list is a property list -
; of even length.
(define (find-href-attribute attr-p-list)
(if (null? attr-p-list)
#f
(let ((attr-name (car attr-p-list))
(attr-value (cadr attr-p-list))
(attr-rest (cddr attr-p-list)))
(if (eq? attr-name 'href)
attr-value
(find-href-attribute attr-rest))))) | An example with property lists that represent HTML attributes in LAML. |