>
>
> It is surprising at first, but since vectors are used so commonly in
>> Clojure instead of lists to represent literal sequential collections of
>> data, it turns out to be extremely convenient to be able to compare it for
>> equality against sequential collections generated as lists or lazy
>> sequences. Basically, all those things are just flat, linear collections,
>> and what we really care about from an equality standpoint is whether the
>> collections have the same elements in the same order. Clojure similarly
>> considers different types of maps (hash-maps, array-maps, sorted-maps) to
>> be equal if the associations are the same. Ditto for hash-sets and
>> sorted-sets.
>>
>>
>>
This comes in handy once you realize that the core functions will sometimes
return different types than you expected:
user=> (type (range 4))
clojure.lang.LazySeq
user=> (reduce conj clojure.lang.PersistentQueue/EMPTY [0 1 2 3])
#<PersistentQueue clojure.lang.PersistentQueue@e44e33f5>
user=> (type '(0 1 2 3))
clojure.lang.PersistentList
user=> (type (subvec [0 1 2 3 4 5] 0 4))
clojure.lang.APersistentVector$SubVector
user=> (type (vals {1 1 2 2 3 3 4 4}))
clojure.lang.APersistentMap$ValSeq
Putting it all together:
user => (= (reduce conj clojure.lang.PersistentQueue/EMPTY [0 1 2 3])
(range 4)
'(0 1 2 3)
(subvec [0 1 2 3 4 5] 0 4)
(vals {0 0 1 1 2 2 3 3}))
true
That right there is real power my friends.
Timothy
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