title: Evaluate expression given as a string
body: <p>I'm curious to know if R can use its <code>eval()</code> function to perform calculations provided by e.g. a string.</p>
  
  <p>This is a common case:</p>
  
  <pre><code>eval("5+5")
  </code></pre>
  
  <p>However, instead of 10 I get:</p>
  
  <pre><code>[1] "5+5"
  </code></pre>
  
  <p>Any solution?</p>