title: formatting decimal number to string with comma as decimal separator in racket
body: <p>Is there any function in racket lang providing convertion of decimal number to string with customized formatting? </p>
  
  <p>I need to format decimal to string formatted as currency style?</p>
  
  <p>Example: Value <code>100.1</code> should become "<code>100,10 CZK"</code></p>