title: How to match a fixed number of characters in ANTLR 3?
body: <p>I want to parse ISO 8601 dates in my ANTLR grammar.</p>
  
  <pre><code>2001-05-03
  </code></pre>
  
  <p>I have the following entries in my grammar file:</p>
  
  <pre><code>date    : FOUR_DIGIT ('-')? TWO_DIGIT ('-')? TWO_DIGIT ;
  
  FOUR_DIGIT
      : TWO_DIGIT TWO_DIGIT ; 
  
  TWO_DIGIT
      : DIGIT DIGIT ;
  
  DIGIT   : ('0'..'9') ;
  </code></pre>
  
  <p>I know I can match one or more with <code>DIGIT+</code> and zero or more with <code>DIGIT*</code></p>
  
  <p>While this works, is there a simpler syntax to specify I want to match exactly 2 <code>DIGIT</code>?</p>