minor nitpick to the answer Sean provided: #{:age} as a function returns
:age for an argument equal to :age and nil for all other inputs, including
a hash map containing that key.
On Sun, May 5, 2019, 22:22 <sheng.peisi....@gmail.com> wrote:
> Thanks. What a newbie question.
>
> 在 2019年5月6日星期一 UTC+8上午11:34:36，se...@corfield.org写道：
>>
>> (sort-by #{:age} …) will use the set #{:age} as the keyfn, and both
>> (#{:age} {:age 3, :name “luo”}) and (#{:age} {:age 1, :name “sheng”}) both
>> return :age – because both maps contain the key in the set. As far as
>> sort-by is concerned, both hash maps compare equal.
>>
>>
>>
>> What you want is (sort-by :age …) so you the keyfn pulls the value
>> corresponding to :age out of the hash maps. That will produce 3 from {:age
>> 3, :name “luo”} and 1 from {:age 1, :name “sheng”} so they will sort
>> appropriately.
>>
>>
>>
>> Sean Corfield -- (970) FOR-SEAN -- (904) 302-SEAN
>> An Architect's View -- http://corfield.org/
>>
>> "If you're not annoying somebody, you're not really alive."
>> -- Margaret Atwood
>>
>>
>>
>> *From: *sheng....@gmail.com
>> *Sent: *Sunday, May 5, 2019 7:48 PM
>> *To: *Clojure
>> *Subject: *results from sort-by are not sorted
>>
>>
>>
>> Hey there,
>>
>>
>>
>> in my lein repl,
>>
>>
>>
>> (sort-by #{:age} [{:age 3,:name "luo"},{:age 1,:name "sheng"}])
>>
>>
>>
>> returns
>>
>>
>>
>> ({:age 3, :name "luo"} {:age 1, :name "sheng"})
>>
>>
>>
>> rather than
>>
>>
>>
>> ({:age 1, :name "sheng"}, {:age 3, :name "luo"}).
>>
>>
>>
>> Why?
>>
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