On Wed, Dec 29, 2010 at 11:55 AM, Laurent PETIT <[email protected]> wrote:
>
>
> 2010/12/29 Ken Wesson <[email protected]>
>>
>> On Wed, Dec 29, 2010 at 11:42 AM, Laurent PETIT <[email protected]>
>> wrote:
>> > 2010/12/29 Ken Wesson <[email protected]>
>> >> (defn insert-into [s x]
>> >> (let [[low high] (split-with #(< % x) s)]
>> >> (concat low [x] high)))
>> >>
>> >> (defn insertion-sort [s]
>> >> (reduce insert-into [] s))
>> >
>> > Hello, just a little 0.00002€ : insert-into will return seqs, so the
>> > reduce
>> > could read :
>> > (reduce insert-into () s)
>> > to make it clear that it's seqs end to end inside insertion-sort
>>
>> It's my habit to use a vector for any "seq literal".
>>
>> How about I split the difference?
>>
>> (reduce insert-into nil s)
>>
>> seems to work just as well. :)
>
> Yeah, not a big deal, it's just that by just reading the line (reduce
> insert-into [] s), I see the initial "collected value" is a vector, and I
> make an assumption about insert-into to return vectors as well.
Eh? I don't. I tend to only assume "it takes seqables" if I see vector
literals going into something. If it's a reduction, I presume the
function being reduced to return seqables as well.
My preference here is for the empty vector:
* The empty list () is odd. In Clojure usually parentheses wrap an
executable expression, not just data.
* Quoting it -- '() -- is just plain ugly.
* The value nil can generally stand in for an empty seq, but has
other unrelated meanings as well.
* The empty vector is, explicitly, a zero-length seqable piece of
inert data.
* So is the empty set #{}, but it's commonplace to use vector
literals as "seq literals", so an empty vector is less confusing.
My objection to the empty set is the same as yours to the empty
vector.
* That goes double for the empty map {}.
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