pe-t">t</a></span></code></dt><dd><p><code>map ~f</code> maps the function <code>f : 'a -&gt; 'b</code> to a function <code>'f T : 'a T -&gt; 'b T</code>.</p><p>As an example, if <code>T (x : u) : u t</code> then <code>map ~(f:u -&gt; v) (T x)</code> is <code>T (f
      x) : v t</code>. As a result, <code>map</code> is often thought of as applying <code>f</code> &quot;in&quot; <code>T</code>.</p><p>The function <code>map</code> is the mapping of arrows, taking every arrow <code>'a -&gt; 'b</code> to an arro