MkOneOf n [m]


DtdToHaskell translates XML DTD into equivalent Haskell types. When there is a choice between different tags, DtdToHaskell uses types like OneOf2, OneOf3, OneOf4, etc. The module Text.XML.HaXml.OneOfN currently defines these types up OneOf20. If your DTD requires larger choices, you can use this program to generate them.

MkOneOf takes an integer N or an integer range N M and writes to the standard output a Haskell module with respectively the datatype OneOfN or the datatypes OneOfN up to and including OneOfM.


If we run "MkOneOf 1 2", the program will print

module Text.XML.HaXml.OneOfN where

import Text.XML.HaXml.Xml2Haskell

data OneOf1 a
    = OneOf1 a
    deriving (Eq,Show)

instance (XmlContent a)
    => XmlContent (OneOf1 a)
    fromElem cs =
        (choice OneOf1
        $ (\c->(Nothing,c))) cs
    toElem (OneOf1 x) = toElem x

data OneOf2 a b
    = OneOf2 a | TwoOf2 b
    deriving (Eq,Show)

instance (XmlContent a,XmlContent b)
    => XmlContent (OneOf2 a b)
    fromElem cs =
        (choice OneOf2 $ choice TwoOf2
        $ (\c->(Nothing,c))) cs
    toElem (OneOf2 x) = toElem x
    toElem (TwoOf2 x) = toElem x



The HaXml library and tools were written by and are copyright to

Copyright © 1998 – 2006 Malcolm Wallace and Colin Runciman

The library incorporates the module Text.ParserCombinators.HuttonMeijerWallace

Copyright © 1996 Graham Hutton and Erik Meijer

with modifications

Copyright © 1998 – 2000 Malcolm Wallace

and may also use or incorporate the module Text.PrettyPrint.HughesPJ

Copyright © 1996 – 1997 John Hughes and Simon Peyton Jones

The HaXml library is licensed under the terms of the GNU Lesser General Public Licence (LGPL), with the following special exception:

As a relaxation of clause 6 of the LGPL, the copyright holders of this library give permission to use, copy, link, modify, and distribute, binary-only object-code versions of an executable linked with the Library, without requiring the supply of any mechanism to modify or replace the Library and relink (clauses 6a, 6b, 6c, 6d, 6e), provided that all the other terms of clause 6 are complied with.

The HaXml tools Xtract, Validate, DtdToHaskell, and MkOneOf, are licensed under the terms of the GNU General Public Licence (GPL).

This library and toolset is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Licences for more details.



This contents of this manual page was copied from the HTML documentation and slightly edited by Arjan Oosting <[email protected]> for the Debian system (but may be used by others).