On Fri, Sep 4, 2015 at 11:30 AM, Gregg Reynolds <d...@mobileink.com> wrote:
> I have a deftype that supports with-meta, but I can't figure out how to
> support caret reader syntax.
>
> To support with-meta, I include a "meta" field and implement IObj methods
> "meta" and "withMeta". Seems to work just fine:
>
> (with-meta (entity-map [:A/B] {:a 1}) {:foo "metadata here"})
>
> But this doesn't work: ^{:foo "metadata there"}(entity-map [:A/B] {:a 1})
>
Ok, so (entity-map...) is passed to the MetaReader as a PersistentList. Of
course. And if I say (def em (entity-map [:A/B] {:a 2})) and then say (def
em2 ^{:foo "bar"} em), then em gets passed as a symbol so the metadata does
not stick.
So it looks like you can only use caret metadata syntax with forms, rather
than types/values. If I wanted my deftype to support caret metadata, I
would have to defined a custom reader syntax for it, which as I understand
is not currently possible. Does that sound accurate?
Then again, the doc says
*Metadata (^)
Metadata is a map associated with some kinds of objects: Symbols, Lists,
Vector, Sets, Maps, tagged literals returning an IMeta, and record, type,
and constructor calls."
So let's try a Symbol:
(symbol? 'a) is true,
(instance? clojure.lang.IMeta 'a) is true, but
(meta ^{:foo 3} 'a) is nil, while
(meta ^{:foo 4} [1 2]) is {:foo 4}
So now I'm confused. Is the documentation just out of sync or am I
misunderstanding something?
Thanks,
Gregg
--
You received this message because you are subscribed to the Google
Groups "Clojure" group.
To post to this group, send email to clojure@googlegroups.com
Note that posts from new members are moderated - please be patient with your
first post.
To unsubscribe from this group, send email to
clojure+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/clojure?hl=en
---
You received this message because you are subscribed to the Google Groups
"Clojure" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to clojure+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
