Challenge 147

2 files changed, 45 insertions, 0 deletions

diff --git a/challenge-147/simon-proctor/raku/ch-1.raku b/challenge-147/simon-proctor/raku/ch-1.raku
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+++ b/challenge-147/simon-proctor/raku/ch-1.raku
@@ -0,0 +1,27 @@
+#!/usr/bin/env raku
+
+use experimental :cached;
+
+#| Display the first 20 base 10 left-truncatable primes
+multi sub MAIN() {
+    .say for (1..*).grep( { is-left-truncatable($_) } )[^20];
+}
+
+multi sub MAIN("test") is hidden-from-USAGE {
+    use Test;
+    ok( is-left-truncatable( 9137 ) );
+    ok( is-left-truncatable( 137 ) );
+    ok( is-left-truncatable( 7 ) );
+    ok( ! is-left-truncatable( 101 ) );
+    ok( ! is-left-truncatable( 8 ) );
+    ok( ! is-left-truncatable( 151 ) );
+    done-testing;
+}
+
+sub is-left-truncatable( UInt \v ) is pure is cached {
+    return False unless v.is-prime;
+    return False if v ~~ /0/;
+    return True if v.codes == 1;
+
+    return is-left-truncatable( v.substr(1).Int );
+}
diff --git a/challenge-147/simon-proctor/raku/ch-2.raku b/challenge-147/simon-proctor/raku/ch-2.raku
new file mode 100644
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+++ b/challenge-147/simon-proctor/raku/ch-2.raku
@@ -0,0 +1,18 @@
+#!/usr/bin/env raku
+
+my @pentagons = (1..*).map( { $_ * ((3 * $_)-1) / 2 });
+
+my @vals = lazy gather {
+    for (0..5000) -> $i {
+        for (0..^$i) -> $j {
+            take (@pentagons[$i], @pentagons[$j], $i+$j);
+        }
+    }
+};
+
+@vals.race.grep(
+    -> (\a, \b, \m) {
+        my \check = Set(@pentagons[^m]);
+        ((a - b) (elem) check) && ((a + b) (elem) check);
+    }
+).map( -> (\a, \b, \m) { ( a, b ) } ).first.say