Hi,
On Mar 8, 9:19 am, alux <alu...@googlemail.com> wrote:
> if I put the same keyword in a map literal multiple times, it seems to
> stay there somehow:
>
> user=> {:a 1 :a 2 :a 3}
> {:a 1, :a 2, :a 3}
This is an optimisation for small maps: the keys are not checked for
uniqueness. One has to distinguish array maps from hash maps. Array
maps are like ye olde alists. For small maps this is faster than a
real hash map. Clojure uses array maps for small map literals (up to
eight keys, IIRC). Having duplicate keys in a map literal is usually
considered a bug.
There is a ticket however, that map literals rely to much on the
reader. So maybe there might be a change here, but I'm not up to date
with that discussion.
Sincerely
Meikel
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