PrimeFactors: Improve triggering (#4149)

* PrimeFactors: Improve triggering
- Added check to regex guard if query matches form "is <number> prime"
- Strips all preceeding non-digit characters from remainder

Fixes #2799

* Added support for new triggers:
- 'is <number> a prime'
- 'is <number> a prime number'
- 'is <number> prime number'

lib/DDG/Goodie/PrimeFactors.pm

@@ -21,7 +21,14 @@ triggers startend => (
     'prime factorization',
     'prime factorization of',
     'factorize',
-    'prime factorize',
+    'prime factorize'
+);
+
+triggers end => (
+    'prime',
+    'a prime',
+    'prime number',
+    'a prime number'
 );
 
 sub convert_to_superscripts (_) {
@@ -88,9 +95,12 @@ sub format_answer {
 }
 
 handle remainder => sub {
-    # Exit if it's not a digit.
+    # Exit if it's not a digit or if it doesn't match the form "is <number> prime"
     # TODO: We should accept different number formats.
-    return unless /^\d+$/;
+    return unless (/^\d+$/ || ($req->query =~ /^is\s\d+\s(a\s)?prime(\snumber)?$/i));
+
+    # Extract only the number from the remainder
+    $_ =~ s/\D+//;
 
     my @factors = factor_exp($_);
 

t/PrimeFactors.t

@@ -42,6 +42,16 @@ ddg_goodie_test(
                                     build_answer('128 - Prime Factors', '2⁷')),
     '42 prime factorize' => test_zci('The prime factorization of 42 is 2 × 3 × 7',
                                     build_answer('42 - Prime Factors', '2 × 3 × 7')),
+    'is 83 prime' => test_zci('83 is a prime number',
+                                    build_answer(undef, '83 is a prime number')),
+    'is 4 prime' => test_zci('The prime factorization of 4 is 2^2',
+                                    build_answer('4 - Prime Factors', '2²')),
+    'is 83 a prime' => test_zci('83 is a prime number',
+                                    build_answer(undef, '83 is a prime number')),
+    'is 83 prime number' => test_zci('83 is a prime number',
+                                    build_answer(undef, '83 is a prime number')),
+    'is 83 a prime number' => test_zci('83 is a prime number',
+                                    build_answer(undef, '83 is a prime number')),
     'optimus prime 45' => undef
 );