Added basic version of bitsum goodie.

lib/DDG/Goodie/Bitsum.pm

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+package DDG::Goodie::Bitsum;
+# ABSTRACT: Write an abstract here
+# Start at https://duck.co/duckduckhack/goodie_overview if you are new
+# to instant answer development
+
+use DDG::Goodie;
+use strict;
+
+zci answer_type => "bitsum";
+zci is_cached   => 1;
+
+# Metadata.  See https://duck.co/duckduckhack/metadata for help in filling out this section.
+name "Bitsum";
+description "Succinct explanation of what this instant answer does";
+primary_example_queries "first example query", "second example query";
+secondary_example_queries "optional -- demonstrate any additional triggers";
+# Uncomment and complete: https://duck.co/duckduckhack/metadata#category
+# category "";
+# Uncomment and complete: https://duck.co/duckduckhack/metadata#topics
+# topics "";
+code_url "https://github.com/duckduckgo/zeroclickinfo-goodies/blob/master/lib/DDG/Goodie/Bitsum.pm";
+attribution github => ["GitHubAccount", "Friendly Name"],
+            twitter => "twitterhandle";
+
+# Triggers
+triggers start => "bitsum", "hammingweight";
+
+# Handle statement
+handle remainder => sub {
+    
+    # optional - regex guard
+    # return unless qr/^\w+/;
+
+    return unless $_; # Guard against "no answer"
+
+    my $n = $_;
+    my $c;
+    for ($c = 0; $n; $n >>= 1) { 
+        $c += $n & 1; 
+    } 
+
+    my $result = $c;
+    
+    return $result,
+        structured_answer => {
+            input     => [html_enc($_)],
+            operation => 'Hamming Weight',
+            result    => html_enc($result),
+        };
+};
+
+
+1;

t/Bitsum.t

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+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use Test::More;
+use DDG::Test::Goodie;
+
+zci answer_type => "bitsum";
+zci is_cached   => 1;
+
+ddg_goodie_test(
+    [qw( DDG::Goodie::Bitsum )],
+    # At a minimum, be sure to include tests for all:
+    # - primary_example_queries
+    # - secondary_example_queries
+    'example query' => test_zci('query'),
+    # Try to include some examples of queries on which it might
+    # appear that your answer will trigger, but does not.
+    'bad example query' => undef,
+);
+
+done_testing;