Scala Parser that sometimes skips whitespace and sometimes does not

I've got a working Scala parser but the solution is not as clean as I would like. The problem is that some of the productions must consider whitespace as part of the token but the "higher-level" productions should be able to ignore/skip the whitespace. If I use the typical scala parser pattern of extending the lower level parsers then the skipWhitespace settings are inherited and things get messy very quickly. I think I would be better off not using the extends approach but rather have an instance of the low level parser available in the higher level parsers' class -- but I'm not sure how to make that work, such that each instance would see only one stream of input characters. Here is part of the lowest-level parser - ``` class VulgarFractionParser extends RegexParsers { override type Elem = Char override val whiteSpace = "".r ``` Then I extend that like ``` class NumberParser extends VulgarFractionParser with Positional { ``` But at this point the NumberParser must explicitly handle whitespace just like the FractionParser. For the NumberParser it is still pretty manageable - but at the next level up I really want to be able to just define productions that do use whitespace as a separator just like a normal regexParser would do. An example would be something like: ``` IBM 33.33/ 1200.00 or IBM 33.33/33.50 1200.00 ``` The 2nd value sometimes has two parts separated by a "/" and sometimes only has a single part with nothing after the slash (or even not containing a slash at all). ``` def bidOrAskPrice = ("$"?) ~> (bidOrAskPrice1 | bidOrAskPrice2 | bidOrAskPrice3) def bidOrAskPrice1 = number ~ ("/".r) ~ number ~ (SPACES) ^^ { case a ~ slash ~ b ~ sp1 => BidOrAsk(a,Some(b)) } def bidOrAskPrice2 = (number ~ "/" ~ (SPACES)) ^^ { case a ~ slash ~ sp => BidOrAsk(a,None) } def bidOrAskPrice3 = (number ~ (SPACES?)) ^^ { case a ~ sp => BidOrAsk(a , None)} ```