[racket] Test to disambiguate x-expression attributes vs. content?

Aha, the xexpr-drop-empty-attributes is probably best, since it will
produce consistent forms. Thanks.

BTW what part of the docs are you citing for *(list* Symbol (option
AttributeList) XexprList)*? The only definition of X-expressions I'm aware
of is here<http://docs.racket-lang.org/xml/index.html?q=x-expression#%28def._%28%28lib._xml%2Fprivate%2Fxexpr-core..rkt%29._xexpr~3f%29%29>
.


On Mon, Jun 10, 2013 at 11:58 AM, Jay McCarthy <jay.mccarthy at gmail.com>wrote:

> The type of Xexpr is...
> | AtomicContent
> | (list* Symbol (option AttributeList) XexprList)
>
> It sounds like you have one function F that you would like to give the
> type "Xexpr -> Value", but you are having a problem when you apply it
> to the AttributeList. You should have such a problem, because an
> AttributeList is not an Xexpr, so your types are wrong.
>
> In other words, if you want to recursively process an Xexpr, then you
> need two functions, one for attribute lists and one for xexpr lists.
>
> Finally, I find it convenient when automatically processing Xexprs to
> ensure that xexpr-drop-empty-attributes is #f so that there is always
> an attribute list and do:
>
> (match xe
>  [(list* tag attrs content) ....])
>
>
>
> On Mon, Jun 10, 2013 at 12:40 PM, Matthew Butterick
> <mb.list.acct at gmail.com> wrote:
> > Consider an x-expression that represents an XML tag, so it has the
> general
> > form
> >
> > '(tag ((attr-name "attr-value") ... ) content ...)
> >
> > The attributes or content might be omitted, of course.
> >
> > When I recursively process these expressions, I start by decomposing the
> > x-expression into components:
> >
> > tag
> > ((attr-name "attr-value") ... )
> > (content ...)
> >
> > The problem that surfaces in a recursive-processing context is that the
> list
> > of content might have the same form as an attribute expression, e.g.,
> >
> > ((field-1 "value-1") (field-2 "value-2"))
> > ((p "some text") (p "some more text"))
> >
> > Is there a test I could use to reliably disambiguate between these two
> > cases, short of creating a new struct for x-expressions? Seems like I'm
> > overlooking some middle ground.
> >
> >
> >
> > ____________________
> >   Racket Users list:
> >   http://lists.racket-lang.org/users
> >
>
>
>
> --
> Jay McCarthy <jay at cs.byu.edu>
> Assistant Professor / Brigham Young University
> http://faculty.cs.byu.edu/~jay
>
> "The glory of God is Intelligence" - D&C 93
>
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