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Truncatable primes: Difference between revisions
Added Racket version
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'''Sample Output'''
<pre>(998443, 739399)</pre>
=={{header|Racket}}==
<lang racket>
#lang racket
(require math/number-theory)
(define (truncate-right n)
(quotient n 10))
(define (truncate-left n)
(define s (number->string n))
(string->number (substring s 1 (string-length s))))
(define (contains-zero? n)
(member #\0 (string->list (number->string n))))
(define (truncatable? truncate n)
(and (prime? n)
(not (contains-zero? n))
(or (< n 10)
(truncatable? truncate (truncate n)))))
; largest left truncatable prime
(for/first ([n (in-range 1000000 1 -1)]
#:when (truncatable? truncate-left n))
n)
; largest right truncatable prime
(for/first ([n (in-range 1000000 1 -1)]
#:when (truncatable? truncate-right n))
n)
; Output:
998443
739399
</lang>
=={{header|REXX}}==
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