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Selecting elements from a given list: `filter'

This abstraction takes a predicate function and a list as its two arguments. The result returned by `filter' is a new list containing all elements of the original list, for which the predicate function returns the value `true'.

(define filter (lambda(p l)
(if (nullp l)
... l))
(cons (car l) (filter p (cdr l)))
(filter p (cdr l))))))

(define l1 (cons one
(cons two
(cons thre...
... nil)))))
(ldisp! (filter (lambda(x) (gtp x two)) l1))
--> 3

Georg P. Loczewski 2004-03-05

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