title: with adder default blocks exercise. How Do I vary output depending if I get a block to my method or not?
body: <p><strong>Here is the rspec I need to pass:</strong></p>
  
  <pre><code>describe "adder" do
     it "adds one to the value returned by the default block" do
   adder do
    5
    end.should == 6
  end
  
  it "adds 3 to the value returned by the default block" do
    adder(3) do
      5
    end.should == 8
   end
  end
  </code></pre>
  
  <p><strong>This is my code</strong></p>
  
  <pre><code>def adder(&amp;block)
  
  if block.call == 5
    block.call + 1
  
  else
  
  block.call + 3
  
  end
  
  end
  </code></pre>
  
  <p><strong>My error output</strong></p>
  
  <p>adder
      adds one to the value returned by the default block
      adds 3 to the value returned by the default block (FAILED - 1)</p>
  
  <p>Failures:</p>
  
  <p>1) some silly block functions adder adds 3 to the value returned by the default block
       Failure/Error: adder(3) do
       ArgumentError:
         wrong number of arguments (1 for 0)
       # ./05_silly_blocks/silly_blocks.rb:5:in <code>adder'
       # ./05_silly_blocks/silly_blocks_spec.rb:37:in</code>block (3 levels) in '</p>