Overloading

     # expression → "(" expression ")" 
     #             | term ("+" expression | nothing)

      $expression = L("(") - $Expression - L(")")
                  | $Term - (L("+") - $Expression | $nothing);

• This looks almost exactly like the grammar rule we're implementing

  • But it's actually Perl code, not a limited sub-language

• We can do similar tricks in SML or Haskell

• I'll use this notation from now on

Next

Copyright © 2007 M. J. Dominus