Easy to explain - absolutely, consistent - mm, not really...
I found this new behavior a bit confusing, imo it breaks principle of
least surprise.
This feature is uncommon in dynamic languages (even Scala allows
duplicate keys - Set('a,'a)/Map('a->1,'a->1)).
Also, from the practical point of view, when prototyping:
- repl: user>(some-fn #{1 ...}) ;just experiment here
- file: #{"http://xyz"; ...} ;bunch of statistical data
In both cases occasional duplicate is not critical.
However, one will be forced to spend extra time on input double-check
and/or deal with error message(s).
-anton
On Jun 25, 5:31 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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>
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