I would say, they treat nil as an empty sequence, which makes nil,
effectively, a unit:
(assoc nil :a :b) ; => {:a :b}
(merge nil {:a :b}) ; => {:a :b}
etc.
On Wednesday, August 29, 2012 7:36:26 PM UTC+2, Moritz Ulrich wrote:
>
> This isn't true in Clojure: http://clojure.org/lisps
>
> However, most functions treat an empty seq as nil because they call `seq'
> on their arguments.
>
> On Wed, Aug 29, 2012 at 6:41 PM, Joop Kiefte <iko...@gmail.com<javascript:>
> > wrote:
>
>> An empty sequence is equal to nil.
>>
>> 2012/8/29 Ambrose Bonnaire-Sergeant <abonnair...@gmail.com <javascript:>
>> >:
>> > My guess is that `merge` has an invariant "if all args are nil, return
>> nil",
>> > making calls to `seq` "contagious" from args to return value.
>> >
>> > => (merge (seq {}) (seq {}))
>> > nil
>> >
>> > Just a guess though.
>> >
>> > Thanks,
>> > Ambrose
>> >
>> > On Thu, Aug 30, 2012 at 12:18 AM, Brian Marick
>> > <mar...@exampler.com<javascript:>>
>> wrote:
>> >>
>> >> Why does `(merge)` return nil? I would have expected it to return the
>> unit
>> >> ({}) by analogy with things like this:
>> >>
>> >> (+) => 0
>> >> (*) => 1
>> >>
>> >> -----
>> >> Brian Marick, Artisanal Labrador
>> >> Contract programming in Ruby and Clojure
>> >> Occasional consulting on Agile
>> >>
>> >>
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