(defmacro abundant-numbers (limit)
  `(filter (macro-to-function is-abundant)
           (gen-list 1 ,limit)))

(defmacro none (predicate lst)
  `(not (some ,predicate ,lst)))

(defmacro take-while (predicate lst)
  `(labels ((take-while-iter (a-lst acc)
              (if (null a-lst)
                  (nreverse acc)
                  (let ((head (car a-lst))
                        (tail (cdr a-lst)))
                    (if (funcall ,predicate head)
                        (take-while-iter tail (cons head acc))
                        (nreverse acc))))))
     (take-while-iter ,lst '())))

(defmacro drop-while (predicate lst)
  `(labels ((drop-while-iter (a-lst)
              (if (null a-lst)
                  a-lst
                  (let ((head (car a-lst))
                        (tail (cdr a-lst)))
                    (if (funcall ,predicate head)
                        (drop-while-iter tail)
                        a-lst)))))
     (drop-while-iter ,lst)))

(defun create-hash-from-list (lst)
  (let ((hash (make-hash-table :test 'equal)))
    (dolist (item lst)
      (setf (gethash item hash) t))
    hash))

(defun is-not-abundant-sum (n abundant-list)
  (let* ((half-n-floor (floor (/ n 2)))
         (first-half (take-while #'(lambda (x) (<= x half-n-floor)) abundant-list))
         (second-half (drop-while #'(lambda (x) (< x half-n-floor)) abundant-list))
         (second-half-to-n (take-while #'(lambda (x) (< x n)) second-half))
         (second-half-hash (create-hash-from-list second-half-to-n)))
    (none (lambda (a)
            (let ((b (- n a)))
              (gethash b second-half-hash)))
          first-half)))

(defun not-abundant-sums-list (limit)
  (let ((abundant-list (abundant-numbers limit)))
    (filter #'(lambda (n)
                (is-not-abundant-sum n abundant-list))
            (gen-list 1 limit))))

CL-USER> (time (sum (not-abundant-sums-list 28123)))
 Evaluation took:
  2.481 seconds of real time
  2.477531 seconds of total run time (2.389778 user, 0.087753 system)
  [ Run times consist of 0.152 seconds GC time, and 2.326 seconds non-GC time. ]
  99.88% CPU
  6,194,100,940 processor cycles
  7,411,226,352 bytes consed
  
4179871

— Me@2024-10-04 03:38:12 PM

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2024.10.05 Saturday (c) All rights reserved by ACHK