ometa Calc {
  digit    = ^digit:d                 -> d.digitValue(),
  number   = number:n digit:d         -> (n * 10 + d)
           | digit,
  addExpr  =  mulExpr:y '+' addExpr:x  -> (x + y)
           | mulExpr:y '-' addExpr:x -> (y - x)
           | mulExpr,
  mulExpr  = mulExpr:x '*' primExpr:y -> (x * y)
           | primExpr:y '/' mulExpr:x -> (y/x)
           | primExpr,
  primExpr = '(' expr:x ')'           -> x
           | number,
  expr     = addExpr
}

Calc.matchAll('6*(4+3)', 'expr')