Solution to task 2

1 files changed, 66 insertions, 0 deletions

diff --git a/challenge-116/jo-37/perl/ch-2.pl b/challenge-116/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(vecsum is_square);
+
+our ($tests, $examples);
+
+run_tests() if $tests || $examples;	# does not return
+
+die <<EOS unless @ARGV;
+usage: $0 [-examples] [-tests] [num]
+
+-examples
+    run the examples from the challenge
+ 
+-tests
+    run some tests
+
+num
+    check if the sum of the squared decimal digits of num is a perfect square
+
+EOS
+
+
+### Input and Output
+
+say 0 + sum_of_squares_is_square(shift);
+
+
+### Implementation
+
+sub sum_of_squares_is_square {
+    local $_ = shift;
+    # Input is restricted to N >= 10:
+    die "not valid\n" unless /^[1-9][0-9]+\z/;
+
+    # The digits are subject to integer operations only, therefore there
+    # are no rounding issues.  Takes a string, not an (internal)
+    # integer.
+    is_square vecsum map $_ * $_, split //;
+}
+
+
+### Examples and tests
+
+sub run_tests {
+    SKIP: {
+        skip "examples" unless $examples;
+        
+        ok sum_of_squares_is_square(34), 'example 1';
+        ok sum_of_squares_is_square(50), 'example 2';
+        ok !sum_of_squares_is_square(52), 'example 3';
+    }
+
+    SKIP: {
+        skip "tests" unless $tests;
+        ok sum_of_squares_is_square(10), 'smallest number for given limit';
+        ok sum_of_squares_is_square(236), 'three nonzero digits';
+        ok sum_of_squares_is_square('1' x 196), '1**2 * 196 == 14**2';
+        ok sum_of_squares_is_square('9' x 81), '9**2 * 81 == 81**2';
+	}
+
+    done_testing;
+    exit;
+}