ometa CalcParser {
  digit = ^digit:d -> d.digitValue(),
  number = number:n digit:d -> (n * 10 + d)
         | digit,
  addExpr = addExpr:x '+' mulExpr:y -> ['add',x,y]
          | addExpr:x '-' mulExpr:y -> ['sub',x,y]
          | mulExpr,
  mulExpr = mulExpr:x '*' primExpr:y -> ['mul',x,y]
          | mulExpr:x '/' primExpr:y -> ['div',x,y]
          | primExpr,
  primExpr = '(' expr:x ')' -> x
           | number:n -> ['num',n],
  expr = addExpr
}

tree = CalcParser.matchAll('6*(4+3)','expr')

ometa CalcInterpreter {
  interp = ['num' anything:x] -> x
         | ['add' interp:x interp:y] -> (x+y)
         | ['sub' interp:x interp:y] -> (x-y)
         | ['mul' interp:x interp:y] -> (x*y)
         | ['div' interp:x interp:y] -> (x/y)
}

CalcInterpreter.match(tree,'interp')