title: Why there is no filter function of Stream in idris?
body: <p>There is <code>filter : (a -&gt; Bool) -&gt; List a -&gt; List a</code> for List, but there is no <code>filter : (a -&gt; Bool) -&gt; Stream a -&gt; Stream a</code> for Stream, why?</p>
  
  <p>Is there some alternatives to do the similar jobs?</p>