John Ky wrote:

Hi,

I've got an object model that I have a difficult time conceptualising how it might look like in Haskell:

class Element { }

class Inline : Element { }

class ParentInline : Inline { List<Inline> children; }

class Bold : ParentInline { } class Underline : ParentInline { }

class Link : ParentInline { String link; }

class Text : Inline { String text; }

class Block : Element { }

class Paragraph : Block { List<Inline> paragraph; }

class Heading : Block { List<Inline> heading; }

class Document : Element { List<Block> blocks; }

How best to represent this OO data model in Haskell? You could, depending on what you intend to do, model a hierarchical document type something like this (if I read your model correctly):

type Document = [Block] data Block = Heading [Inline] | Paragraph [Inline] data Inline = Text String | ParentInline data ParentInline = PIL PILType [Inline] data PILType = Bold | Underline | Link String Does that fit? -k

John, For the particular object model that you are interested in (an HTML- ish object model), you should check out the paper by Peter Thiemann entitled "A Typed Representation for HTML and XML Documents in Haskell". -- Robin Bate Boerop http://robin.bateboerop.name On 7-Dec-06, at 8:07 AM, John Ky wrote:

Hi,

I've got an object model that I have a difficult time conceptualising how it might look like in Haskell:

class Element { }

class Inline : Element { }

class ParentInline : Inline { List<Inline> children; }

class Bold : ParentInline { } class Underline : ParentInline { }

class Link : ParentInline { String link; }

class Text : Inline { String text; }

class Block : Element { }

class Paragraph : Block { List<Inline> paragraph; }

class Heading : Block { List<Inline> heading; }

class Document : Element { List<Block> blocks; }

How best to represent this OO data model in Haskell?

Thanks

-John