We can search for a value in a string and replace it with another value using the clojure.string/replace function. The first parameter is the original string value that we want to replace parts of. The second parameter can be a string value or regular expression. The last parameter is the replacement value that can be a string value or a function that returns a string value. The function itself gets either a string argument if the match has no nested groups (when match is a regular expression) or a vector with a complete match followed by the nested groups when the match has nested groups.
In the following example we several invocation of the clojure.string/replace function with different arguments:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 | (ns mrhaki.string.replace (:require [clojure.string :as str] [clojure.test :refer [is]]));; Example string value to do replacements on.(def s "Programming with Clojure is fun!");; Match argument can be a string value,;; that gives same result as java.lang.String#replace method.(is (= "Programming with Clojure is awesome!" (str/replace s "fun" "awesome") (.replace s "fun" "awesome")));; Match argument can also be regular expression pattern.(is (= "Programming_with_Clojure_is_fun!" (str/replace s #"\s+" "_")));; When the regular expression pattern has groups;; we can refer to them using $ followed by matched;; group number, eg. $1 for the first group.(is (= "Execution 1 took 200ms" (str/replace "run1=200ms" #"run(\d+)=(\d+ms)" "Execution $1 took $2")));; Replace argument can be a function.;; Argument of the function is string of entire match;; if there are no nested groups.(is (= "[NOTE] [CAUTION]" (str/replace "[note] [caution]" #"\[\w+\]" #(.toUpperCase %))));; Otherwise if there are nested groups a vector is;; used as argument for the replacment function;; where the first argument is the;; entire match followed by the nested groups.(is (= "ABC def" (str/replace "abc DEF" #"(\w+)(\s+)(\w+)" #(str (.toUpperCase (% 1)) (% 2) (.toLowerCase (% 3))))));; By destructuring the vector argument;; we can refer to the groups using a name.(defn replacement [[_ execution time]] (let [seconds (/ (bigdec time) 1000)] (str "Execution " execution " took " seconds " seconds")))(is (= "Execution 1 took 0.2 seconds" (str/replace "run1=200ms" #"run(\d+)=(\d+)ms" replacement))) |
Written with Clojure 1.10.1.
