Implement Parser#comp

Author: leocassarani

lib/parser.rb

@@ -42,6 +42,12 @@ def dest
     end
   end
 
+  def comp
+    current
+      .split('=').last
+      .split(';').first
+  end
+
   private
 
   attr_reader :lines, :current

spec/unit/parser_spec.rb

@@ -242,7 +242,8 @@
       'D=D-M'   => 'D-M',
       'M=M-D'   => 'M-D',
       'M=D&M'   => 'D&M',
-      'M=D|M'   => 'D|M'
+      'M=D|M'   => 'D|M',
+      'D=0;JMP' => '0'
     }.each do |command, mnemonic|
       context "when the comp mnemonic is #{mnemonic}" do
         let(:input) { command }