title: How to create a set of words from a string?
body: <p>I'm writing my first program.</p>
  <p>I need to know how to create a set of unique words from a string.</p>
  <p>I want to know how to do this to be able to know the number of elements in the set (or the number of unique words in the string)</p>
  <p>I would need this to happen:</p>
  <p><em>input:</em></p>
  <p><strong>string=(&quot;one one two three three four hello hello&quot;)</strong></p>
  <p><em>output:</em></p>
  <p><strong>(&quot;one&quot;, &quot;two&quot;, &quot;three&quot;, &quot;four&quot;, &quot;hello&quot;)</strong></p>