prefix parser.cs

void Operand()
{
  if(matches(TokenId.Identifier, TokenId.LiteralValue))
  {
    match(TokenId.Identifier, TokenId.LiteralValue);
  }
  else
    Expr();
}

void Expr()
{
  match(TokenId.Plus, TokenId.Minus, ...);
  Operand();
  Operand();
}

// "matches" should verify that the lookahead is one of the list provided
//    as its argument.  If it is, it should return true.  otherwise false.
// "match" should verify that the lookahead is one of the list provided
//    as its argument.  It should consume the token if it matches, and set
//    the lookahead to the next token from the string.  If it doesn't match
//    it should throw and give a message that the parse failed while expecting
//    one of the tokens passed as the argument (in a normal parser).