[ANN] Clojure 1.9.0-alpha4
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Stuart Halloway
May 31, 2016, 11:42:00 AM5/31/16
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Clojure 1.9.0-alpha4 is now available.
Try it via
- Leiningen: [org.clojure/clojure "1.9.0-alpha4"]
1.9.0-alpha4 includes the following changes since 1.9.0-alpha3:
- fix describe empty cat
- improve update-in perf
- optimize seq (&) destructuring
Rich Hickey
Jun 1, 2016, 10:17:14 AM6/1/16
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To give people an idea of the update-in and seq destructuring improvements:
(let [d3 {:a {:b {:c 2}}}]
(dotimes [_ 10]
(time (dotimes [_ 10000000]
(update-in d3 [:a :b :c] inc)))))
;;;;;;;;;;; 1.9 alpha3 ;;;;;;;;;;;;;;
user=> "Elapsed time: 6489.189065 msecs"
"Elapsed time: 6501.518961 msecs"
"Elapsed time: 6479.994554 msecs"
"Elapsed time: 6477.236659 msecs"
"Elapsed time: 6490.542382 msecs"
"Elapsed time: 6494.044657 msecs"
"Elapsed time: 6475.188285 msecs"
"Elapsed time: 6498.734628 msecs"
"Elapsed time: 6486.312312 msecs"
"Elapsed time: 6476.566904 msecs"
nil
;;;;;;;;;;; 1.9 alpha4 ;;;;;;;;;;;;;;
user=> "Elapsed time: 1613.631053 msecs"
"Elapsed time: 1614.271583 msecs"
"Elapsed time: 1607.393994 msecs"
"Elapsed time: 1605.966032 msecs"
"Elapsed time: 1605.731867 msecs"
"Elapsed time: 1605.836779 msecs"
"Elapsed time: 1617.090363 msecs"
"Elapsed time: 1611.065741 msecs"
"Elapsed time: 1611.249945 msecs"
"Elapsed time: 1624.351585 msecs"
nil
(let [v (into [] (range 1000000))]
(dotimes [_ 10]
(time (dotimes [_ 10]
(loop [[x & xs] v]
(if xs
(recur xs)
x))))))
;;;;;;;;;;; 1.9 alpha3 ;;;;;;;;;;;;;;
user=> "Elapsed time: 1531.858419 msecs"
"Elapsed time: 1521.997662 msecs"
"Elapsed time: 1499.931748 msecs"
"Elapsed time: 1499.745901 msecs"
"Elapsed time: 1496.63342 msecs"
"Elapsed time: 1499.363234 msecs"
"Elapsed time: 1506.309383 msecs"
"Elapsed time: 1514.943316 msecs"
"Elapsed time: 1534.90731 msecs"
"Elapsed time: 1524.550125 msecs"
nil
;;;;;;;;;;; 1.9 alpha4 ;;;;;;;;;;;;;;
user=> "Elapsed time: 155.544283 msecs"
"Elapsed time: 131.861647 msecs"
"Elapsed time: 141.774727 msecs"
"Elapsed time: 238.939786 msecs"
"Elapsed time: 294.832594 msecs"
"Elapsed time: 278.476703 msecs"
"Elapsed time: 133.259029 msecs"
"Elapsed time: 139.917267 msecs"
"Elapsed time: 137.444001 msecs"
"Elapsed time: 147.852057 msecs”
nil
The code now produced for [x & xs] style destructuring is now as good as the best first/next code you could write by hand, while the code produced for [x y z] destructuring of indexed items is the same (fast, indexed) as always.
Rich
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(let [d3 {:a {:b {:c 2}}}]
(dotimes [_ 10]
(time (dotimes [_ 10000000]
(update-in d3 [:a :b :c] inc)))))
;;;;;;;;;;; 1.9 alpha3 ;;;;;;;;;;;;;;
user=> "Elapsed time: 6489.189065 msecs"
"Elapsed time: 6501.518961 msecs"
"Elapsed time: 6479.994554 msecs"
"Elapsed time: 6477.236659 msecs"
"Elapsed time: 6490.542382 msecs"
"Elapsed time: 6494.044657 msecs"
"Elapsed time: 6475.188285 msecs"
"Elapsed time: 6498.734628 msecs"
"Elapsed time: 6486.312312 msecs"
"Elapsed time: 6476.566904 msecs"
nil
;;;;;;;;;;; 1.9 alpha4 ;;;;;;;;;;;;;;
user=> "Elapsed time: 1613.631053 msecs"
"Elapsed time: 1614.271583 msecs"
"Elapsed time: 1607.393994 msecs"
"Elapsed time: 1605.966032 msecs"
"Elapsed time: 1605.731867 msecs"
"Elapsed time: 1605.836779 msecs"
"Elapsed time: 1617.090363 msecs"
"Elapsed time: 1611.065741 msecs"
"Elapsed time: 1611.249945 msecs"
"Elapsed time: 1624.351585 msecs"
nil
(let [v (into [] (range 1000000))]
(dotimes [_ 10]
(time (dotimes [_ 10]
(loop [[x & xs] v]
(if xs
(recur xs)
x))))))
;;;;;;;;;;; 1.9 alpha3 ;;;;;;;;;;;;;;
user=> "Elapsed time: 1531.858419 msecs"
"Elapsed time: 1521.997662 msecs"
"Elapsed time: 1499.931748 msecs"
"Elapsed time: 1499.745901 msecs"
"Elapsed time: 1496.63342 msecs"
"Elapsed time: 1499.363234 msecs"
"Elapsed time: 1506.309383 msecs"
"Elapsed time: 1514.943316 msecs"
"Elapsed time: 1534.90731 msecs"
"Elapsed time: 1524.550125 msecs"
nil
;;;;;;;;;;; 1.9 alpha4 ;;;;;;;;;;;;;;
user=> "Elapsed time: 155.544283 msecs"
"Elapsed time: 131.861647 msecs"
"Elapsed time: 141.774727 msecs"
"Elapsed time: 238.939786 msecs"
"Elapsed time: 294.832594 msecs"
"Elapsed time: 278.476703 msecs"
"Elapsed time: 133.259029 msecs"
"Elapsed time: 139.917267 msecs"
"Elapsed time: 137.444001 msecs"
"Elapsed time: 147.852057 msecs”
nil
The code now produced for [x & xs] style destructuring is now as good as the best first/next code you could write by hand, while the code produced for [x y z] destructuring of indexed items is the same (fast, indexed) as always.
Rich
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Isaac Zeng
Jun 1, 2016, 12:12:04 PM6/1/16
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That really cool
Frank Castellucci
Jun 1, 2016, 7:49:00 PM6/1/16
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Ghadi Shayban
Jun 2, 2016, 12:52:04 PM6/2/16
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Let bindings from thbe macroexpansion of (let [[x & xs] v] ...)
;; old macroexpand
[G__1 v
vec__2 G__1
x (nth vec__2 0 nil)
xs (nthnext vec__2 1)]
;; new macroexpand
[G__6 v
vec__7 G__6
seq__8 (seq vec__7)
first__9 (first seq__8)
seq__8 (next seq__8)
x first__9
xs seq__8]
676c...@gmail.com
Jun 4, 2016, 2:28:24 AM6/4/16
to Clojure
This isn’t only an optimisation but also a change in behaviour, isn’t
it?
Clojure 1.9.0-alpha3:
user=> (let [[x & xs] #{1 2 3}] x)
UnsupportedOperationException nth not supported on this type: PersistentHashSet clojure.lang.RT.nthFrom (RT.java:948)
Clojure 1.9.0-alpha4:
user=> (let [[x & xs] #{1 2 3}] x)
1
Perhaps the documentation needs to be updated?
http://clojure.org/reference/special_forms#_vector_binding_destructuring
--
David
it?
Clojure 1.9.0-alpha3:
user=> (let [[x & xs] #{1 2 3}] x)
UnsupportedOperationException nth not supported on this type: PersistentHashSet clojure.lang.RT.nthFrom (RT.java:948)
Clojure 1.9.0-alpha4:
user=> (let [[x & xs] #{1 2 3}] x)
1
Perhaps the documentation needs to be updated?
http://clojure.org/reference/special_forms#_vector_binding_destructuring
--
David
Atamert Ölçgen
Jun 4, 2016, 2:33:47 AM6/4/16
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On Sat, Jun 4, 2016 at 9:28 AM, <676c...@gmail.com> wrote:
This isn’t only an optimisation but also a change in behaviour, isn’t
it?
Clojure 1.9.0-alpha3:
user=> (let [[x & xs] #{1 2 3}] x)
UnsupportedOperationException nth not supported on this type: PersistentHashSet clojure.lang.RT.nthFrom (RT.java:948)
Clojure 1.9.0-alpha4:
user=> (let [[x & xs] #{1 2 3}] x)
1
I hope this will be considered a regression and the old behavior will be restored.
Perhaps the documentation needs to be updated?
http://clojure.org/reference/special_forms#_vector_binding_destructuring
--
David
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Alex Miller
Jun 4, 2016, 8:22:38 AM6/4/16
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Why?
Alan Forrester
Jun 4, 2016, 8:28:55 AM6/4/16
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What are you asking “Why?” about? You haven’t quoted anything so it’s not clear what you’re asking about.
Alan
On 4 Jun 2016, at 13:22, Alex Miller <al...@puredanger.com> wrote:
> Why?
Alan
On 4 Jun 2016, at 13:22, Alex Miller <al...@puredanger.com> wrote:
> Why?
Nicola Mometto
Jun 4, 2016, 8:33:20 AM6/4/16
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How is this a regression?
It doesn't cause any code that used to work to stop working.
The fact that tail destructuring now causes non-sequential collections to be destructured by sequential destructuring should be just considered an instance of GIGO and an implementation detail.
It doesn't cause any code that used to work to stop working.
The fact that tail destructuring now causes non-sequential collections to be destructured by sequential destructuring should be just considered an instance of GIGO and an implementation detail.
Atamert Ölçgen
Jun 4, 2016, 12:32:09 PM6/4/16
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Hi Alex,
Because unordered collections shouldn't have heads defined.
Is (first #{3 1 2}) => 3? or 2? or 1?
(I just tried it in a REPL and it is apparently 1.)
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Martin Raison
Jun 4, 2016, 4:15:45 PM6/4/16
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I support this change. Not only is it closer to the GIGO philosophy, but "let x in S" is actually a very reasonable use-case. Sometimes I just want an element from a set and I don't care about which particular one.
Your code may break if you're using try/catch to handle sets in a special way, but I can't imagine a situation where using clojure.core/set? wouldn't be simpler and more appropriate.
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