check if a number is - , + or x
<p>How can I check if a number has a <code>-</code>, <code>+</code>, <code>x</code> or nothing in front of it?</p>

<p>Options to check would be:</p>

<pre><code>20
+20
-20
x20
</code></pre>

<p>20 being any number.</p>
