string - clojure 删除字符串中模式的最后一个入口

Question

我在字符串的末尾有一个字符串和一些模式。我如何才能在单词的末尾准确地删除此模式，但即使它存在于开头或中间，也仅此而已。例如，字符串是

PatternThenSomethingIsGoingOnHereAndLastPattern

我需要在最后删除“模式”，这样结果就会是

PatternThenSomethingIsGoingOnHereAndLast

我怎样才能做到这一点？

Answer 1

您的问题没有指定模式是否必须是正则表达式或纯字符串。在后一种情况下，您可以使用简单的方法：

(defn remove-from-end [s end]
  (if (.endsWith s end)
      (.substring s 0 (- (count s)
                         (count end)))
    s))

(remove-from-end "foo" "bar") => "foo"
(remove-from-end "foobarfoobar" "bar") => "foobarfoo"

有关正则表达式的变体，请参阅Dominic Kexel 的答案。

Answer 2

您可以使用replaceAll

=> (.replaceAll "PatternThenSomethingIsGoingOnHereAndLastPattern" "Pattern$" "")
"PatternThenSomethingIsGoingOnHereAndLast"

或者clojure.string/replace

=> (clojure.string/replace "PatternThenSomethingIsGoingOnHereAndLastPattern" #"Pattern$" "") "PatternThenSomethingIsGoingOnHereAndLast"

Answer 3

你需要的一切我都相信

(def string "alphabet")
(def n 2)
(def m 4)
(def len (count string))

;starting from n characters in and of m length;
(println
 (subs string n (+ n m)))              ;phab
;starting from n characters in, up to the end of the string;
(println
 (subs string n))                      ;phabet
;whole string minus last character;
(println
 (subs string 0 (dec len)))            ;alphabe
;starting from a known character within the string and of m length;
(let [pos (.indexOf string (int \l))]
  (println
   (subs string pos (+ pos m))))     ;lpha
;starting from a known substring within the string and of m length.
(let [pos (.indexOf string "ph")]
  (println
   (subs string pos (+ pos m))))      ;phab