It probably does an "identical?" call on a pair before calling
compare, for efficiency. In other words, it may "work" on non-
comparable types, but only when passed n instances of the exact same
object:
user> (sorted-set '(1) '(1))
; Exception
user> (let [x '(1)] (sorted-set x x))
#{(1)}
This is almost certainly not documented behavior and should not be
relied upon.
Cheers,
Jason
On Feb 20, 11:42 am, Frantisek Sodomka <[email protected]> wrote:
> It looks that it is more complicated than that:
> user=> (sorted-set () ())
> #{()}
> user=> (sorted-set {} {})
> #{{}}
> user=> (sorted-set #{} #{})
> #{#{}}
>
> Frantisek
>
> On 20 Ún, 20:33, Vincent Foley <[email protected]> wrote:
>
> > I'm pretty sure that sorted-set works only with values that are
> > instances of a class that implements Comparable.
>
> > user=> (instance? Comparable [])
> > true
> > user=> (instance? Comparable {})
> > false
> > user=> (instance? Comparable ())
> > false
> > user=>
>
> > On Feb 20, 2:21 pm, Frantisek Sodomka <[email protected]> wrote:
>
> > > sorted-set works for vectors, but doesn't work for lists, maps and
> > > sets:
> > > user=> (sorted-set [1 4])
> > > #{[1 4]}
> > > user=> (sorted-set [1 4] [1 4])
> > > #{[1 4]}
> > > user=> (sorted-set [4 1] [1 4])
> > > #{[1 4] [4 1]}
>
> > > user=> (sorted-set '(1 4))
> > > #{(1 4)}
> > > user=> (sorted-set '(1 4) '(1 4))
> > > java.lang.ClassCastException: clojure.lang.PersistentList cannot be
> > > cast to java.lang.Comparable (NO_SOURCE_FILE:0)
>
> > > user=> (sorted-set {:a 1 :b 2})
> > > #{{:a 1, :b 2}}
> > > user=> (sorted-set {:a 1 :b 2} {:a 1 :b 2})
> > > java.lang.ClassCastException: clojure.lang.PersistentArrayMap cannot
> > > be cast to java.lang.Comparable (NO_SOURCE_FILE:0)
>
> > > user=> (sorted-set #{1 2})
> > > #{#{1 2}}
> > > user=> (sorted-set #{1 2} #{1 2})
> > > java.lang.ClassCastException: clojure.lang.PersistentHashSet cannot be
> > > cast to java.lang.Comparable
> > > (NO_SOURCE_FILE:0)
>
> > > ---
> > > How does sorted-set know which value is bigger or smaller? Could this
> > > functionality be exported?
> > > user=> (sorted-set [4 3] [2 1])
> > > #{[2 1] [4 3]}
> > > user=> (> [4 3] [2 1])
> > > java.lang.ClassCastException: clojure.lang.LazilyPersistentVector
> > > cannot be cast to java.lang.Number (NO_SOURCE_FILE:0)
> > > user=> (= [4 3] [2 1])
> > > false
>
> > > user=> (> "xyz" "abc")
> > > java.lang.ClassCastException: java.lang.String cannot be cast to
> > > java.lang.Number (NO_SOURCE_FILE:0)
>
> > > Thank you, Frantisek
>
>
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