While there are other possible uses
(example<https://twitter.com/borkdude/status/302881431649128448>),
I see myself mainly using as-> as a mechanism for resorting to thread-last
within a thread-first expression.
For example, given
(-> [[1 1 1] 2 3] (nth 0))
I might want to add an operation that doesn't happen to have an adequate
signature (sequence functions tend to not be thread-first friendly). You
can't just add:
(-> [[1 1 1] 2 3] (nth 0) (map inc)) ;; fail
And neither can be solved by adding a lambda:
(-> [[1 1 1] 2 3] (nth 0) #(map inc %)) ;; fail
Clojure 1.5's as->, though, can come to the rescue.
(-> [[1 1 1] 2 3] (nth 0) (as-> x (map inc x))) ;; cool
Now, I only wish 1.5 came with as->> macro! Its implemetation is trivial
anyway.
(defmacro as->> [name & body]
(let [[b v] ((juxt butlast last) body)]
`(let [~name ~v]
~@b)))
(->> [1 2 3] (as->> _ (nth _ 0)))
Of course, for the given examples, using these "as" forms is overkill. But
if you've ever ended up writing large expressions (especially when
experimenting) which arbitrarily nest/interleave ->> and ->, using as-> and
as->> can provide a more sequential, structured alternative.
Couldn't find any related discussion about the uses of as->, as its name is
unfriendly to Google/JIRA searches. Thoughts?
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