ebnf = r"""
    expr = (number ws?)* 
    number = factor additive*
    additive = ("+"/"-") factor
    factor = primary multiplicative*
    multiplicative = ("*" / "/") primary
    primary = parens / neg / number
    parens   = "(" number ")"
    neg = "-" primary 
    number = ((~"[0-9]"+ "."? ~"[0-9]"*) / ("." ~"[0-9]"+)) (("e"/"E") ("-"/"+") ~"[0-9]"+)?
    ws        = ~"\s*"
    lpar      = "("
    rpar      = ")"
    lbra      = "["
    rbra      = "]"
    lcbra     = "{"
    rcbra     = "}"
    lt        = "<"
    gt        = ">"
    comma     = ","
    octup     = "^"
    octdown   = "_"
    barsign   = "|"
    plus = "+"
    minus = "-"
    times = "*"
    div   = "/"
    emptyline = ws+
    """