On Dec 11, 9:08 pm, Chouser <chou...@gmail.com> wrote:
> On Thu, Dec 11, 2008 at 7:49 PM, Robert Koberg <r...@koberg.com> wrote:
>
> > Hi,
>
> > Would it be desirable to further define keywords such that it allows a
> > special kind of namespacing.
>
> > * This could allow for more efficient (for the user) and targeted
> > navigation over large, nested collections.
> > * It would allow for mixing related data that might need to be treated
> > in different ways.
> > * It could provide the building blocks for a collection transformation
> > language
>
> > For example:
>
> > :keyword or :nil:keyword - defines a keyword in a null namespace
> > -- keeps backward compatibility
> > -- equivalent to the XML element <foo/> (no namepsace defined)
>
> > ::keyword - defines a namespaced keyword in a default namespace
> > -- equivalent to the XML element <foo xmlns="http://some/namespace"/>
>
> > :myns:keyword - defines a namespaced keyword in a named namespace
> > -- equivalent to the XML element <foo xmlns:myns="http://some/namespace
> > "/>
>
> > Perhaps a requirement for this type of thing would be that the
> > namespaces need to be declared on the root element of the (nested)
> > collection.
>
> Keywords can already be namespace-qualified:
>
> user=> (namespace :foo)
> nil
> user=> (namespace :my-ns/foo)
> "my-ns"
> user=> (namespace ::foo)
> "user"
>
> The idea of using this feature to specify XML namespaces has been
> discussed. Rich even adjusted the reader rules to allow fully-qualified
> URLs as namespaces:
>
> user=> (namespace :http://n01se.net/chouser/tag)
> "http://n01se.net/chouser";
>
> This should allow something to parse XML and produce a tree of Clojure
> collections representing it with full namespace qualifications, though to my
> knowledge this hasn't been done yet.
It would be a convenience for some of my work if it were legal to do
(derive :foo :bar) using unqualified keywords. I don't know enough yet
about Clojure to know what that might break. In Common Lisp, the text
":FOO" is guaranteed always to be turned into a reference to the exact
same keyword object, a symbol in the KEYWORD package whose name is
"FOO"; I don't know what the rules are in Clojure about keywords
without namespaces. Perhaps they're like uninterned symbols; I don't
know.
I'm building a type system for classifying lots of hunks of data and
selecting appropriate operations for them, and derive is nice for
that, but it's a minor inconvenience to have to namespace-qualify all
those typenames. It's nice that I *can* qualify them by namespace; it
isn't always nice that I *have* to.
That said, it doesn't prevent me from getting anything done, it's just
a sort of pebble in my shoe sometimes.
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