Solution to task 1

1 files changed, 82 insertions, 0 deletions

diff --git a/challenge-155/jo-37/perl/ch-1.pl b/challenge-155/jo-37/perl/ch-1.pl
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+++ b/challenge-155/jo-37/perl/ch-1.pl
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+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use bigint;
+use Math::Prime::Util qw(next_prime is_prime);
+use Coro::Generator;
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [N]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+N
+    Print the first N distinct fortunate numbers in ascending order.
+
+EOS
+
+
+### Input and Output
+
+main: {
+    my $fn = gen_fortunate_numbers();
+    my %fn;
+    # Collect the first N distinct fortunate numbers.
+    until (keys %fn == $ARGV[0]) {
+        $fn{$fn->()} = undef;
+    }
+    # Present in ascending order.
+    say for sort {$a <=> $b} keys %fn;
+}
+
+
+### Implementation
+
+# Build a generator for fortunate numbers.  The resulting sequence is
+# neither sorted nor does it consist of distinct values only.
+sub gen_fortunate_numbers {
+    my $pn = 1;
+    my $p = 1;
+
+    generator {
+        while () {
+            $pn *= ($p = next_prime($p));
+            for (my $m = 2;; $m++) {
+                yield($m), last if is_prime($pn + $m);
+            }
+        }
+    }
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+
+        my $fn = gen_fortunate_numbers();
+        is [map $fn->(), 1 .. 9], [3, 5, 7, 13, 23, 17, 19, 23, 37],
+            'the raw sequence: neither sorted nor distinct'
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+
+        my $fn = gen_fortunate_numbers();
+        $fn->() for 1 .. 57;
+        is $fn->(), 331, '#58 according to OEIS';
+	}
+
+    done_testing;
+    exit;
+}