clojure remove last entrance of pattern in string

Question

I have a string and some pattern at the end of the string. How can I remove this pattern exactly at the end of the word but nothing more even if it exists in the beginning or in the middle. For example, the string is

PatternThenSomethingIsGoingOnHereAndLastPattern

and I need to remove the "Pattern" at the end so that result would be

PatternThenSomethingIsGoingOnHereAndLast

How can I do that?

Answer 1

Your question doesn't specify if the pattern has to be a regex or a plain string. In the latter case you could just use the straightforward approach:

(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"

For a regex variation, see the answer of Dominic Kexel.