I agree that duplicate keys in literals are probably a coder error but
IMO this deserves some kind of compiler warning rather than an error.
You're going to get into lots of sticky situations otherwise that only
confuse people if the semantics are different between literals and
other usage. Simple is good.
On Jun 25, 3:31 pm, Stuart Halloway <stuart.hallo...@gmail.com> wrote:
> Duplicate keys in maps/sets are disallowed in literals and factory functions,
> where data is generally literal & inline and therefore likely represents
> coder error:
>
> ; all disallowed
> #{:a :a}
> {:a 1 :a 2}
> (hash-map :a 1 :a 2)
> (hash-set :a :a)
>
> They are allowed in other contexts, where the data could come from anywhere:
>
> ; dumb, but these forms not generally called with a literal
> (set [:a :a])
> (into #{} [:a :a])
>
> I find this behavior consistent and easy to explain, but I was involved in
> the design conversation so maybe I have participant blindness. :-)
>
> Stu
>
>
>
> > On Fri, 25 Jun 2010 15:36:31 +0200
> > Michael Wood <esiot...@gmail.com> wrote:
>
> >> On 25 June 2010 12:27, Tim Robinson <tim.blacks...@gmail.com> wrote:
> >>> I tried Clojure via Githhub today.
>
> >>> Anyone notice this bug that hadn't existed in Version 1.1
>
> >>> user=> #{:item1 {:a "A" :b "B"} :item2 {:a "A" :b "B"}}
> >>> java.lang.IllegalArgumentException: Duplicate key: {:a "A", :b "B"}
>
> >> You're trying to put duplicate values into a set.
>
> > So? Most places, putting a value that's already in a set into the set
> > is a nop. Even in clojure that exhibits the above behavior:
>
> > user=> #{:a :a}
> > java.lang.IllegalArgumentException: Duplicate key: :a
> > user=> (set [:a :a])
> > #{:a}
> > user=> (conj #{:a} :a)
> > #{:a}
> > user=>
>
> > Apparently, duplicate keys in sets are only disallowed in set
> > literals. Arguably, that must be a mistake on the users part, but
> > it sure seems to clash with the behavior of sets elsewhere.
>
> > <mike
> > --
> > Mike Meyer <m...@mired.org>
> > http://www.mired.org/consulting.html
> > Independent Network/Unix/Perforce consultant, email for more information.
>
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