^x attaches the metadata to a form *before* it is evaluated. The with-meta
function attaches the metadata to a form *after* it's been evaluated.
Generally speaking, the ^x form is used for attaching metadata used by
macros and the Clojure compiler, whereas with-meta is used to attach
run-time metadata to Clojure data structures.
- James
On 8 May 2014 13:34, Pascal Germroth <funkyco...@gmail.com> wrote:
> Hi,
>
> I'm trying to attach metadata to some values (not the vars holding them).
> I thought ^{x} y was the same as (with-meta y {x}), but while it works for
> f2/f4, f1's metadata is nowhere to be found, while f3 works as expected:
>
> (def f1 "doc" ^{:x 1} (partial inc))
> (meta f1) ; nil, unexpected
> (meta #'f1) ; contains :doc, but not :x, as expected
>
> (def f2 "doc" ^{:x 2} #(inc %))
> (meta f2) ; {:x 2}, as expected
> (meta #'f2) ; contains :doc, but not :x, as expected
>
> (def f3 "doc" (with-meta (partial inc) {:x 3}))
> (meta f3) ; {:x 3}
>
> (def f4 "doc" (with-meta #(inc %) {:x 4}))
> (meta f4) ; {:x 4}
>
> Cheers,
>
> --
> pascal
>
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