Created
January 9, 2020 04:47
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Walrus operator in Python 3.8 vs if-let macro in Clojure
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dev> (if-let [coll (seq [1 2 3])] | |
(println coll) | |
(println "EMPTY")) | |
(1 2 3) | |
nil | |
dev> (if-let [coll (seq [])] | |
(println coll) | |
(println "EMPTY")) | |
EMPTY | |
nil | |
;; macro expansion | |
dev> (macroexpand-1 | |
'(if-let [coll (seq [1 2 3])] | |
(println coll) | |
(println "EMPTY"))) | |
(clojure.core/let | |
[temp__5733__auto__ (seq [1 2 3])] | |
(if | |
temp__5733__auto__ | |
(clojure.core/let [coll temp__5733__auto__] (println coll)) | |
(println "EMPTY"))) |
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In [1]: if coll := [1, 2, 3]: | |
...: print(coll) | |
...: else: | |
...: print('EMPTY') | |
...: | |
[1, 2, 3] | |
In [2]: if coll := []: | |
...: print(coll) | |
...: else: | |
...: print('EMPTY') | |
...: | |
EMPTY | |
# prior to version 3.8 | |
In [3]: coll = [1, 2, 3] | |
In [4]: if coll: | |
...: print(coll) | |
...: else: | |
...: print('EMPTY') | |
...: | |
[1, 2, 3] |
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