I am building a description of page state using a list of pageStyles
> data PageStyle= Orientation Orient
> | Margin BoxData
> | Border BoxData
> | CurrentYPos Float
> | CurrentXPos Float
To extract particular items from the current pagestate, I create functions
of the form:
> border [] = error "no border in page"
> border (a:xs) = case a of
> Border x -> x
> otherwise -> border xs
It would be much nicer if I could create a generalized form of this like:
> border p = extract Border "no border in page" p
But the extract function appears to be illegal:
> extract f s [] = error s
> extract f s (a:xs) = case a of
> f x -> x
> otherwise -> extract f s xs
Is there another way of getting this functionality?
-Alex-
___________________________________________________________________
S. Alexander Jacobson i2x Media
1-212-697-0184 voice 1-212-697-1427 fax
