On 25 February 2009, Adrian Cuthbertson wrote:
>
> Hmm, I get a stack overflow when trying that make macro.
> After using macroexpand-1...
> (with-meta (struct stuff 1 2) {:type (keyword (str *ns*) (name (quote
> stuff)))})
> I still get the stack overflow.
>
> I'm on svn 1307, jdk 1.5 mac osx.
> Any ideas?
Hmmm... On svn 1307, I get the same stack overflow. No issue on svn 1280. It's
the keyword :type as metadata...but only when stringifying the value to output
it.
(def x (with-meta [1 2] {:type "hi"})) ; define but don't print: works
(meta x) ; get metadata: works
(get x 1) ; get a value: works
(println x) ; stack overflow
(str x) ; stack overflow
(format "%s" x) ; stack overflow
If the keyword in the macro is changed to anything other than "type", there's
no issue.
(with-meta [] {:typeX "hi"}) ; no worries
(with-meta [] {:type "hi"}) ; stack overflow
String representation obviously uses :type now in a very particular way. I'm
not sure where this happens though. Can anyone shed some light on the details?
-Jeff
>
> On Thu, Feb 26, 2009 at 7:08 AM, Jeff Valk <[email protected]> wrote:
> >
> > How about appending type metadata automagically...
> >
> > (defstruct stuff :a :b)
> > (defmacro make
> > "Creates a new instance of struct t and appends 'type' t as metadata"
> > [t & vs]
> > `(with-meta
> > (struct ~t ~...@vs)
> > {:type (keyword (str *ns*) (name '~t))}))
> >
> > user> (make stuff 1 2)
> > {:a 1, :b 2}
> >
> > user> (meta (make stuff 1 2))
> > {:type :user/stuff}
> >
> > -Jeff
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