Hi all,
I find the proposed function let-> in Clojure 1.5 very useful, but a bit
ugly. The arguments are backwards when compared to vanilla let, and it
doesn't support destructuring where it easily could (which I believe would
be helpful when threading 'state-like' maps, as I find let-> very useful
for).
I'd like to float an alternative implementation which improves on both
these issues. Thoughts?
(defmacro new-let->
"Establishes bindings as provided for let, evaluates the first form
in the lexical context of that binding, then re-establishes bindings
to that result, repeating for each successive form"
[bindings & forms]
(assert (vector? bindings) "binding must be a vector")
(assert (= 2 (count bindings)) "binding vector must contain exactly two
forms")
`(let [~@bindings
~@(interleave (repeat (bindings 0)) (drop-last forms))]
~(last forms)))
(new-let-> [{:keys [foo bar] :as state} {:foo 1 :bar 2}]
(assoc state :foo (inc bar))
(assoc state :bar (inc foo))) ; => {:foo 3, :bar 4}
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*Alex Nixon*
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