title: Regex for decimal numbers
body: <p>Could anybody provide a regular expression for a number that has to be between 1 and 17 in length, and could optionally contain a mantissa of up to 4 places? The length of 17 includes both the characteristic and the mantissa.</p>
  
  <p>Edit:</p>
  
  <p>The length of 17 excludes the decimal point. </p>
  
  <p>Valid examples: </p>
  
  <pre>
  12345678901234567 
  1234567890123.4567 
  123456789012345.67
  12.34
  </pre>
  
  <p>Invalid:</p>
  
  <pre>
  12345678901234.5678 (Length of numerals = 18)
  </pre>
  
  <p>Thanks.</p>