Re: [Haskell-cafe] hxt pickling question

On Thu, 24 Jan 2013 17:05:15 +0100 Erik Hesselink wrote:

There's showPickled [0] and unpickleDoc [1], maybe those help?

Thank you , they help a lot :-) I was stuck looking in Text.XML.HXT.Arrow.Pickle for the answer and got lost trying to decipher IOStateArrow s a XmlTree and runX. It's odd that there does not seem to be a way to use the example so that a tree can be written directly to a file. xpickleDocument :: PU a -> SysConfigList -> String -> IOStateArrow s a XmlTreeSource store an arbitray value in a persistent XML document Except there doesn't seem to be a way to pass that value into xpickleDocument without reading a document first using xunpickleDocument. Thanks again. Brian

Erik

[0] http://hackage.haskell.org/packages/archive/hxt/latest/doc/html/Text-XML-HXT... [1] http://hackage.haskell.org/packages/archive/hxt/latest/doc/html/Text-XML-HXT...

On Thu, Jan 24, 2013 at 4:40 PM, wrote:

...

Hi,

Trying to understand how to write a document using a pickler but I can't make sense of the types.

From the example:

runX ( xunpickleDocument xpSeason [ withValidate no , withTrace 1 , withRemoveWS yes , withPreserveComment no ] "simple2.xml" >>> processSeason >>> xpickleDocument xpSeason [ withIndent yes ] "new-simple2.xml" )

So all I want to do is pickle a value directly instead of reading the value from a document. I expected to do something like:

runX (someHXTPicklingFunction myValue >>> xpickleDocument ...)

but I can't seem to figure out what someHXTPicklingFunction should be, it's certainly nothing obvious like pickleDoc, because that generates the wrong value.

Seems like I probably have a much more fundamental problem in that I really don't understand how the arrow part of this little example really works, but I was kind of hoping that doing something "simple" like this might shed some light on that. And then was immediately stuck in type hell.

Thanks,

Brian

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