Text.XML.Expat.Pickle

A two-way pickler/unpickler that pickles a ''t'' to type ''a''. See Text.XML.Expat.Tree for the tree structure as used with ''t''. ''t'' can be Node, [Node], [(String,String)], (String,String) or String.

A PU_ can be composed using the pickler primitives defined in this module.

Constructors

PU (t -> Either String a) (a -> t -> t)

type PU a = PU_ Node a

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In the most common case, where the part of the tree you're pickling/unpickling is of type Node, you can use PU and maintain source code compatibility with HXT. In other cases you will need to use PU_, which will break compatibility.

pickleXML :: Maybe Encoding -> PU_ Node a -> a -> ByteString

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Pickle a Haskell data structure to XML text. Outputs a strict ByteString.

unpickleXML :: PU_ Node a -> Maybe Encoding -> ByteString -> Either String a

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Unpickle XML text to a Haskell data structure. Takes a lazy ByteString.

class XmlPickler t a where

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Takes one more argument than the HXT version of XmlPickler, which is the type of the part of the tree, like PU_ does.

Methods

xpickle :: PU_ t a

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Instances

Stringable s => XmlPickler s Integer

Stringable s => XmlPickler s Int

XmlPickler Node a => XmlPickler Node ([] a)

pickleTree :: PU a -> a -> Node

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unpickleTree :: PU a -> Node -> Either String a

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Pickler primitives

xpReadShow :: (Stringable s, Read n, Show n) => PU_ s n

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Convert an XML string <-> a type that implements Read and Show.

xpText0 :: Stringable t => PU_ t String

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Convert XML text <-> String. Handles empty strings.

xpText :: Stringable t => PU_ t String

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Convert XML text <-> String. Empty strings result in unpickle failure.

xpElem :: Nodeable t => String -> PU_ Node a -> PU_ t a

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Create/parse an XML element of the specified name. Fails if an element of this name can't be found at this point in the tree. This implementation unpickles elements of different names in any order, while HXT's xpElem will fail if the XML order doesn't match the Haskell code.

xpAttr :: String -> PU_ (String, String) a -> PU_ Node a

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Create/parse an XML attribute of the specified name. Fails if the attribute can't be found at this point in the tree.

xpOption :: PU_ t a -> PU_ t (Maybe a)

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Convert XML text - a Maybe type. During unpickling, Nothing is returned if there's a failure during the unpickling of the first argument.

xpPair :: PU_ t a -> PU_ t b -> PU_ t (a, b)

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Convert XML text <-> a 2-tuple using the two arguments.

xpTriple :: PU_ t a -> PU_ t b -> PU_ t c -> PU_ t (a, b, c)

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Convert XML text <-> a 3-tuple using the three arguments.

xp4Tuple :: PU_ t a -> PU_ t b -> PU_ t c -> PU_ t d -> PU_ t (a, b, c, d)

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Convert XML text <-> a 4-tuple using the four arguments.

xp5Tuple :: PU_ t a -> PU_ t b -> PU_ t c -> PU_ t d -> PU_ t e -> PU_ t (a, b, c, d, e)

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Convert XML text <-> a 5-tuple using the five arguments.

xpList :: PU_ Node a -> PU_ Node [a]

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Convert XML text <-> a list of elements. During unpickling, failure of the argument unpickler is the end-of-list condition (and it isn't a failure).

xpWrap :: (a -> b, b -> a) -> PU_ t a -> PU_ t b

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Apply a lens to convert the type of your data structure into something that the pickler primitives can handle (such as tuples).

xpWrapMaybe :: (a -> Maybe b, b -> a) -> PU_ t a -> PU_ t b

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xpWrapEither :: (a -> Either String b, b -> a) -> PU_ t a -> PU_ t b

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xpAllAttrs :: Attrable t => PU_ t [(String, String)]

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xpAlt

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::
=> a -> Int	Selector
-> [PU_ t a]
-> PU_ t a
Allow alternative picklers. Selector function is used during pickling, but unpickling is done by trying each list element in order until one succeeds.