Solution to task 2

1 files changed, 57 insertions, 0 deletions

diff --git a/challenge-150/jo-37/perl/ch-2.pl b/challenge-150/jo-37/perl/ch-2.pl
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+++ b/challenge-150/jo-37/perl/ch-2.pl
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+#!/usr/bin/perl -s
+
+use v5.16;
+use Test2::V0;
+use Math::Prime::Util qw(factor_exp vecmax);
+use Coro::Generator;
+
+our $examples;
+
+run_tests() if $examples;	# does not return
+
+die <<EOS unless @ARGV == 1;
+usage: $0 [-examples] [N]
+
+-examples
+    run the examples from the challenge
+
+N
+    Print first N square-free integers.
+
+EOS
+
+
+### Input and Output
+
+main: {
+    my $sq_free = gen_square_free();
+    say $sq_free->() for 1 .. $ARGV[0];
+}
+
+
+### Implementation
+
+# Build a generator for square-free integers.
+sub gen_square_free {
+    generator {
+        # Treat 1 separately as factor(1) returns an empty list.
+        yield 1;
+        for (my $n = 2;; $n++) {
+            # Check if the maximum exponent in N's factorization is one.
+            yield $n if 1 == vecmax map $_->[1], factor_exp $n;
+        }
+    }
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    my $sq_free = gen_square_free();
+    is [map $sq_free->(), 1 .. 19],
+        [1, 2, 3, 5, 6, 7, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 26, 29, 30],
+        'example 1';
+
+    done_testing;
+    exit;
+}