egison-3.3.11: sample/primes.egi

;;;
;;;
;;; Pattern-matching against sequence of natural numbers
;;;
;;;

;; Extract all twin primes from the infinite list of prime numbers with pattern-matching!
(define $twin-primes
  (match-all primes (list integer)
    [<join _ <cons $p <cons ,(+ p 2) _>>>
     [p (+ p 2)]]))

;; Enumerate first 10 twin primes
(take 10 twin-primes)

;; Extract all prime-triplets from the infinite list of prime numbers with pattern-matching!
(define $prime-triplets
  (match-all primes (list integer)
    [<join _ <cons $p
              <cons (& $m (| ,(+ p 2) ,(+ p 4)))
               <cons ,(+ p 6) _>>>>
     [p m (+ p 6)]]))

;; Enumerate first 10 twin primes
(take 10 prime-triplets)