title: How to specify method default argument using define_method?
body: <p><code>define_method</code> could be used to define methods:</p>
  
  <pre><code>define_method(:m) do |a|
  end
  </code></pre>
  
  <p>which is equivalent to the following: </p>
  
  <pre><code>def m(a)
  end
  </code></pre>
  
  <p>However, what is the equivalent form of the following using <code>define_method</code>:</p>
  
  <pre><code>def m(a=false)
  end
  </code></pre>
  
  <p><em>Note that I'd need to be able to call <code>m()</code> without giving any argument.</em></p>