; common/math.clj
(defn nths
"Returns a collection of values for each idx in idxs. Throws an error if any one idx is out of bounds."
[coll idxs]
(map #(nth coll %) idxs))
; nrepl
common.math> (try (/ 1 0)
(catch Exception e (prn "in catch"))
(finally (prn "in finally")))
"in catch"
"in finally"
nil
common.math> (try (nths '(5 6 7 8 9) '(0 5))
(catch Exception e (prn "in catch"))
(finally (prn "in finally")))
"in finally"
IndexOutOfBoundsException clojure.lang.RT.nthFrom (RT.java:784)
common.math> (nths '(5 6 7 8 9) '(0 1 3))
(5 6 8)
common.math> *clojure-version*
{:major 1, :minor 5, :incremental 0, :qualifier "alpha4"}
我无法弄清楚第二个表达式出了什么问题。我期待它会再次打印:
"in catch"
"in finally"
运行单元测试时也会发生同样的情况:
lein test unittest.common.math
FAIL in (test-nths) (math.clj:87)
expected: (thrown? IndexOutOfBoundsException (nths (quote (5 6 7 8 9)) (quote (0 5))))
actual: nil
应该会通过。
最佳答案
Nths 是惰性的,因此当您的 repl 尝试打印结果时,该函数实际上会运行:
core> (def result (try (nths '(5 6 7 8 9) '(0 5))
(catch Exception e (prn "in catch"))
(finally (prn "in finally"))))
"in finally"
#'core/result
core> result
; Evaluation aborted.
您可以在nths
中捕获异常,或者在使用它时更有意义地捕获它
rsadl.core> (def result (try (nths '(5 6 7 8 9) '(0 5))
(catch Exception e (prn "in catch"))
(finally (prn "in finally"))))
"in finally"
#'core/result
core> (try (println result) (catch Exception e (prn "in catch")))
("in catch"
nil
或者正如 number23_cn 指出的那样,只要您不需要它因其他原因而变得懒惰,您就可以在创建它时实现结果。
关于clojure - 不同类型的异常没有被捕获?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/12151302/