From 51824d2766f87125585d722ddfaa404b118fc5d8 Mon Sep 17 00:00:00 2001
From: Jag Talon <jagtalon@duckduckgo.com>
Date: Sun, 30 Mar 2014 13:40:57 -0400
Subject: [PATCH] PrimeFactors: Added new features:

- Use `factor_exp` instead of `factor`.
- Add commify to format the input.
- Add exponents to the primes. It's much easier to read.
---
 lib/DDG/Goodie/PrimeFactors.pm | 69 +++++++++++++++++++++++++++-------
 t/PrimeFactors.t               | 18 +++++----
 2 files changed, 66 insertions(+), 21 deletions(-)

diff --git a/lib/DDG/Goodie/PrimeFactors.pm b/lib/DDG/Goodie/PrimeFactors.pm
index ba3c8a327..7b2dc8b8d 100644
--- a/lib/DDG/Goodie/PrimeFactors.pm
+++ b/lib/DDG/Goodie/PrimeFactors.pm
@@ -2,7 +2,8 @@ package DDG::Goodie::PrimeFactors;
 #Returns all the prime factors of the entered number
 
 use DDG::Goodie;
-use Math::Prime::Util 'factor';
+use Math::Prime::Util 'factor_exp', 'is_prime';
+use utf8;
 
 zci answer_type => "prime_factors";
 zci is_cached => 1;
@@ -24,20 +25,62 @@ topics 'math';
 category 'calculations';
 attribution github => [ 'https://github.com/austinheimark', 'austin_heimark' ];
 
-handle remainder => sub {
-	return unless /^\d+$/;
-	my @factors = factor($_);
+# This adds exponents to the prime numbers.
+# It outputs both text and HTML:
+# - 2^2
+# - 2<sup>2</sup>
+sub format_exp {
+    my $factor = shift;
 
-	my $result;
+    if($factor->[1] > 1) {
+	return "$factor->[0]^$factor->[1]", "$factor->[0]<sup>$factor->[1]</sup>";
+    }
+    return $factor->[0], $factor->[0];
+}
+
+# This goes through all the prime factors and formats them in an "n × m" format.
+# It outputs both text and HTML.
+sub format_prime {
+    my @factors = @_;
+    my @text_result = ();
+    my @html_result = ();
+
+    foreach my $factor (@factors) {
+	my ($text, $html) = format_exp($factor);
 	
-	# If it has only one factor then it is a prime. Except if it's 0 or 1.
-	if(@factors == 1 && $_ > 1) {
-	    $result = "$_ is a prime number.";
-	} else {
-	    $result = "The prime factors of $_ are " . join(', ', @factors) . '.';
-	}
-	
-	return $result, 'html' => "$result";
+	push(@text_result, $text);
+	push(@html_result, $html);
+    }
+
+    return join(" × ", @text_result), join(" × ", @html_result);
+}
+
+# This adds commas to the number.
+# It converts 10000000 to 10,000,000.
+# It was copied from http://perldoc.perl.org/perlfaq5.html#How-can-I-output-my-numbers-with-commas-added%3f
+sub commify {
+    local $_  = shift;
+    1 while s/^([-+]?\d+)(\d{3})/$1,$2/;
+    return $_;
+}
+
+handle remainder => sub {
+    # Exit if it's not a digit.
+    # TODO: We should accept different number formats.
+    return unless /^\d+$/;
+    my @factors = factor_exp($_);
+    my $formatted = commify($_);
+
+    # If it has only one factor then it is a prime. Except if it's 0 or 1.
+    my $result;
+    if(is_prime($_)) {
+	return "$formatted is a prime number.", html => "$formatted is a prime number.";
+    } else {
+	my ($text, $html) = format_prime(@factors);
+	my $intro = "The prime factorization of $formatted is";
+
+	return "$intro $text", html => "$intro $html";
+    }
 };
 
 1;
diff --git a/t/PrimeFactors.t b/t/PrimeFactors.t
index 0e949b036..6fdc48ca5 100644
--- a/t/PrimeFactors.t
+++ b/t/PrimeFactors.t
@@ -2,6 +2,8 @@
 
 use strict;
 use warnings;
+use utf8;
+
 use Test::More;
 use DDG::Test::Goodie;
 
@@ -12,14 +14,14 @@ ddg_goodie_test(
 	[qw(
 		DDG::Goodie::PrimeFactors
 	)],
-    '72 prime factors' => test_zci('The prime factors of 72 are 2, 2, 2, 3, 3.', 
-				   html => 'The prime factors of 72 are 2, 2, 2, 3, 3.'),
-    'prime factors of 111' => test_zci('The prime factors of 111 are 3, 37.', 
-				       html => 'The prime factors of 111 are 3, 37.'),
-    'prime factors of 30' => test_zci('The prime factors of 30 are 2, 3, 5.', 
-				      html => 'The prime factors of 30 are 2, 3, 5.'),
-    'prime factorization of 45' => test_zci('The prime factors of 45 are 3, 3, 5.',
-					    html => 'The prime factors of 45 are 3, 3, 5.'),
+    '72 prime factors' => test_zci('The prime factorization of 72 is 2^3 × 3^2', 
+				   html => 'The prime factorization of 72 is 2<sup>3</sup> × 3<sup>2</sup>'),
+    'prime factors of 111' => test_zci('The prime factorization of 111 is 3 × 37', 
+				       html => 'The prime factorization of 111 is 3 × 37'),
+    'prime factors of 30' => test_zci('The prime factorization of 30 is 2 × 3 × 5', 
+				      html => 'The prime factorization of 30 is 2 × 3 × 5'),
+    'prime factorization of 45' => test_zci('The prime factorization of 45 is 3^2 × 5',
+					    html => 'The prime factorization of 45 is 3<sup>2</sup> × 5'),
     'optimus prime 45' => undef,
 );