Clojure 中记录的模式匹配
Pattern matching on records in Clojure
现在支持吗?我能找到的唯一信息是来自 wiki 的示例 (https://github.com/clojure/core.match/wiki/Deftype-and-defrecord-matching)
产生错误:
CompilerException java.lang.AssertionError: Invalid list syntax (Red.
(Red. a x b) y c) in (Black. (Red. (Red. a x b) y c) z d). Valid
syntax: [[:default :guard] [:or :default] [:default :only] [:default
:seq] [:default :when] [:default :as] [:default :<<] [:default
:clojure.core.match/vector]]
这还没有实现,但由于记录的行为类似于地图,您可以这样做:
(defrecord ab [a b])
user.ab
user> (let [x (->ab 1 1)]
(match [x]
[{:a _ :b 2}] :a0
[{:a 1 :b 1}] :a1
[{:c 3 :d _ :e 4}] :a2
:else nil))
:a1
也可以在记录的类型上进行匹配,但有点不雅
user> (let [x (->ab 1 1)
aba user.ab]
(match [(type x) x]
[aba {:a _ :b 2}] :a0
[aba {:a 1 :b 1}] :a1
[aba {:c 3 :d _ :e 4}] :a2
:else nil))
:a1
https://github.com/clojure/core.match/wiki/Basic-usage#map-patterns
现在支持吗?我能找到的唯一信息是来自 wiki 的示例 (https://github.com/clojure/core.match/wiki/Deftype-and-defrecord-matching) 产生错误:
CompilerException java.lang.AssertionError: Invalid list syntax (Red. (Red. a x b) y c) in (Black. (Red. (Red. a x b) y c) z d). Valid syntax: [[:default :guard] [:or :default] [:default :only] [:default :seq] [:default :when] [:default :as] [:default :<<] [:default :clojure.core.match/vector]]
这还没有实现,但由于记录的行为类似于地图,您可以这样做:
(defrecord ab [a b])
user.ab
user> (let [x (->ab 1 1)]
(match [x]
[{:a _ :b 2}] :a0
[{:a 1 :b 1}] :a1
[{:c 3 :d _ :e 4}] :a2
:else nil))
:a1
也可以在记录的类型上进行匹配,但有点不雅
user> (let [x (->ab 1 1)
aba user.ab]
(match [(type x) x]
[aba {:a _ :b 2}] :a0
[aba {:a 1 :b 1}] :a1
[aba {:c 3 :d _ :e 4}] :a2
:else nil))
:a1
https://github.com/clojure/core.match/wiki/Basic-usage#map-patterns