First commit for choose goodie

lib/DDG/Goodie/Combinations.pm

@@ -0,0 +1,39 @@
+package DDG::Goodie::Combinations;
+
+use DDG::Goodie;
+
+triggers any => 'choose';
+zci is_cached => 1;
+zci answer_type => 'combination';
+
+primary_example_queries '5 choose 3';
+description 'Returns the number of combinations of size k which can be made from n objects (nCk).';
+attribution github => ['https://github.com/conorfl', 'conorfl'],
+twitter => '@areuhappylucia';
+code_url 'https://github.com/duckduckgo/zeroclickinfo-goodies/blob/master/lib/DDG/Goodie/Combinations.pm';
+topics 'math';
+category 'calculations';
+
+handle remainder => sub {
+    s/^\s+//;
+    s/\s+$//;
+    if($_ =~ /^(\d+)(?:\s+)(\d+)$/){
+        if($2 > $1){
+            return $1 . " choose " . $2 . " = 0";
+        }
+        my $n = $1; 
+
+        my $k = $2;
+        my $combi = 1;
+        for my $i (($k+1)..$n) {
+            $combi *= $i;
+        }
+        for my $j (1..($n-$k)){
+            $combi /= $j
+        }
+        return $n . " choose " . $k . " = " . $combi;
+    }
+    return $_;
+};
+
+1;