LISP list Clisp function smaller than

Question

I want to write a function that takes two arguments an atom x and a list L and returns a list of numbers in list L that are smaller than x

like for example:

List is (2 10 3 9 4 8) and x is 5

Output should be: (2 3 4)

I guess i can use the less than function

(defun less-than (x y)
  (or (< x y))

but it returns less than from the list :(

What is your code to filter the list? Have you seen (remove-if inverted-pred list)? — reto
– reto, Commented Dec 4, 2013 at 22:56
@Sylwester But inverting the predicate is so easy: (remove-if (complement #'pred) ...) :) — Joshua Taylor
– Joshua Taylor, Commented Dec 4, 2013 at 23:18
@JoshuaTaylor Nice that it's more than one way to skin a cat :) — Sylwester
– Sylwester, Commented Dec 5, 2013 at 1:38

uselpa · Accepted Answer · 2013-12-04 23:04:53Z

1

(defun less-than (x L)
  (remove-if-not
   (lambda (e) (< e x))
   L))

(less-than 5 '(2 10 3 9 4 8))
=> (2 3 4)

or

(defun less-than (x L)
  (remove-if
   (lambda (e) (>= e x))
   L))

answered Dec 4, 2013 at 23:04

uselpa

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1 Comment

Because remove-if-not works with general sequences, the answer also works with vectors. (less-than 5 #(2 10 3 9 4 8)).