June 2018 Update

Task/Truncatable-primes/Factor/truncatable-primes.factor

@@ -0,0 +1,36 @@
+USING: formatting fry grouping.extras kernel literals math
+math.parser math.primes sequences ;
+IN: rosetta-code.truncatable-primes
+
+CONSTANT: primes $[ 1,000,000 primes-upto reverse ]
+
+: number>digits ( n -- B{} ) number>string string>digits ;
+
+: no-zeros? ( seq -- ? ) [ zero? not ] all? ;
+
+: all-prime? ( seq -- ? ) [ prime? ] all? ;
+
+: truncate ( seq quot -- seq' ) call( seq -- seq' )
+    [ 10 digits>integer ] map ;
+
+: truncate-right ( seq -- seq' ) [ head-clump ] truncate ;
+
+: truncate-left ( seq -- seq' ) [ tail-clump ] truncate ;
+
+: truncatable-prime? ( n quot -- ? ) [ number>digits ] dip
+    '[ @ all-prime? ] [ no-zeros? ] bi and ; inline
+
+: right-truncatable-prime? ( n -- ? ) [ truncate-right ]
+    truncatable-prime? ;
+
+: left-truncatable-prime? ( n -- ? ) [ truncate-left ]
+    truncatable-prime? ;
+
+: find-truncatable-primes ( -- ltp rtp )
+    primes [ [ left-truncatable-prime?  ] find nip ]
+           [ [ right-truncatable-prime? ] find nip ] bi ;
+
+: main ( -- ) find-truncatable-primes
+    "Left: %d\nRight: %d\n" printf ;
+
+MAIN: main