Why are refs metadata rather than tags?

[weavejester]

I'm curious why refs are metadata, and everything else uses tags. Is there a reason for this?

[malcolmsparks]

EDN tag literals are like macros and great for immediate read-time
evaluation but you. Refs are (potentially) something you want to process
prior to them being elided by the reader. That's the primary rationale.
It's not set in stone.

I'm curious why refs are metadata, and everything else uses tags. Is there
a reason for this?

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[malcolmsparks]

On my phone. Will fix up when back at a kb sorry!

[weavejester]

Ah, that makes a lot of sense! Thanks for the quick response.

Still, metadata is data about data, whereas a tag alters the meaning or "type" of the data. Given this, would #ref [:foo :bar] be semantically better than ^:ref [:foo :bar]?

[gardnervickers]

@weavejester I tend to agree that it should be a tag instead of metadata, however the implementation needs to still set a metadata flag on the returned value and be processed by walking down the tree and calling get-in on the partially resolved tree. We need to do this because there's not really a way to "walk back up the tree" to follow a path back down during read-time.

[weavejester]

I was thinking that you could just create a "ref" placeholder type, and then walk the tree afterwards.

For example:

(defrecord Ref [keys])

(defmethod reader 'ref [_ _ value]
  (->Ref value))

(defn resolve-refs [config]
  (walk/postwalk #(if (instance? Ref %) (get-in config (:keys %)) %) config))

[malcolmsparks]

I agree that ref metadata feels wrong now. Let's reconsider it and test an alternative approach prior to 1.0 final. I definitely not married to the ^:ref syntax and it feels a little inconsistent.

[SevereOverfl0w]

This can now be considered done I think. #ref now works.

[xiongtx]

README should be updated with #ref.

[timgilbert]

#45 updates the README.

[malcolmsparks]

This has been implemented. They are now tags.