/*
  Hi Amit, I fixed a bug in your code: you had

    dig = (charRange '0' '9'),

  (which means "invoke charRange, then match the character '0', then match the character '9'), but you actually meant

    dig = charRange('0', '9')

  -Alex
*/

ometa Calc {
charRange x y = char:c ?(c >= x) ?(c <= y) -> c,
dig = charRange('0', '9'),
num = dig+,
fac = fac:x '*' num:y -> (x * y) 
    | fac:x '/' num:y -> (x / y)
    | num,
exp = exp:x '+' fac:y -> (x + y)
    | exp:x '-' fac:y -> (x - y)
    | fac
}

a = (((4 / 5))*6)
b = a * 4.4
b * 2