clojure删除字符串中模式的最后一个入口

Question

我有一个字符串和字符串末尾的一些模式。我如何准确地删除单词末尾的这个模式，但即使它存在于开头或中间，也不会有更多的东西。例如，字符串为

PatternThenSomethingIsGoingOnHereAndLastPattern

我需要去掉结尾处的"Pattern“，这样结果就是

PatternThenSomethingIsGoingOnHereAndLast

我该怎么做呢？

Answer 1

您的问题没有指定模式必须是正则表达式还是普通字符串。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answer of Dominic Kexel。

Answer 2

您可以使用replaceAll

模式模式(.replaceAll "PatternThenSomethingIsGoingOnHereAndLastPattern“”

=> $“)

"PatternThenSomethingIsGoingOnHereAndLast“

或clojure.string/replace

替换模式(clojure.string/

"PatternThenSomethingIsGoingOnHereAndLastPattern“#”$ "") =>

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