(defpackage #:lt-examples
  (:use #:cl #:lambda-tools))

(enable-partial-eval-reader-macro)


;; http://rosettacode.org/wiki/Luhn_test_of_credit_card_numbers 
(defun luhn (n)
  (>> n #'reverse
      #$(map 'list #'digit-char-p $char)
      #$(mapcar #'*
                (loop :for i :upto (length $digits) :collect (1+ (mod i 2)))
                $digits)
      #$(mapcar #$$(if (> $$x 9) (- $$x 9) $$x) $digits)  ;; <-- nested partial eval
      #$(zerop (mod (apply #'+ $digits) 10))))



(enable-lazy-eval-reader-macros)

(defun lazy-eg1 ()
  (let* ((four #~(print (+ 2 2)))
         (sum #~(+ (print 1) (print 2) (print 3) #!four)))
    (list #!sum #!sum)))

;; prints 
;; 1 
;; 2 
;; 3 
;; 4 

;; returns
;; (10 10)