[Haskell-cafe] hxt: How to Unpickle Multiple Adjacent Elements

[Michael Orlitzky]

On 01/04/2015 06:15 PM, Jimmy Lu wrote:
> Hi,
> 
> With xml element having DTD like following:
> 
>     <!ELEMENT entry ((art*, formula?, table?), hw, hsl?, (pr | altpr)?, (ahw, hsl?, (pr | altpr)?)*, vr?, fl?, lb*, in*, ((dx) | (cx?, def?))?, dro*, dxnl*, uro*, syns*)>
> 
> I want to unpickle the sequence
> 
>     hw, hsl?, (pr | altpr)?, (ahw, hsl?, (pr | altpr)?)*
> 
> into Haskell data type [Headword] where

Are you asking how to extract ONLY that sequence? If so, it's not
possible: you have to provide a pickler/unpickler for the whole thing,
and then ignore the parts you don't want.

That aside, you might not want to make a list out of the elements you've
shown. That's a sequence of a fixed number of heterogeneous things. The
first one is an "hw", the second is an "(optional) hsl", the third is an
"(optional) pr or altpr",...

The last expression with the star is what you'd want to (un)pickle into
a list.