Clojure的reduce函数如何工作以反转列表而不是向量

Question

I was looking at ways to reverse a collection using Clojure without using the reverse function and stumbled upon this solution.

(reduce conj '() [1 2 3 4 5]) => (5 4 3 2 1) 

I have read the Clojure api with regard to how reduce works but am still baffled as to how it is working in this instance.

Also I have found if I were to pass a vector as the third argument instead of a list ie:

(reduce conj [] [1 2 3 4 5]) => [1 2 3 4 5]

I seem to get back the same vector.

I was wondering if anybody could give me a brief explanation as to to how reduce is working in both instances.

Also I have found this method also reverses a vector:

(into () [1 2 3 4]) => (4 3 2 1) ; ???

Answer 1

The doc string says: conj[oin]. Returns a new collection with the xs 'added'. (conj nil item) returns (item). The 'addition' may happen at different 'places' depending on the concrete type.

For a vector, the natural place to add is the end. For a list, the natural place to add is the front (as with 'cons').