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What is the replace-first method in Clojure regular expression?

Chinweuba Elijah Azubuike

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

What is a regular expression?

A regular expression is a character sequence or code format used in search patterns to streamline the search results of a string. We mainly use it in the string search algorithm.

What is the replace-first method?

The replace-first method in Clojure replaces the first occurrence of a matched pattern with a substring in a parent string.

Syntax

(replace-first string pattern replacestr)
Syntax of the replace-first method in Clojure

Parameters

The replace-first method receives three parameters following the syntax above.

  1. string: This is the parent string containing a substring to be matched.
  2. pattern: This is the pattern to be built.
  3. replacestr: This is the string we replace with the parent string after matching the pattern.

Return value

The replace-first method returns a string value.

Example

(ns clojure.examples.example
(:gen-class))
(defn func []
(def pattern (re-pattern "\\d+"))
(def newstring (clojure.string/replace-first "sam409uel134" pattern "993"))
(println newstring))
(func)
An example of the replace-first method in Clojure

Explanation

  • Line 4: We create a func function.
  • Line 5: We build our pattern using the re-pattern method (re-pattern "\\d+") and save it to the pattern variable
  • Line 6: We carry out our string replacement following the syntax above using clojure.string/replace-first. The replace-first method matches the number sequences in the string. Then, it replaces the first occurrence, 409, with the replace string, 993, in the sam409uel134 string.
  • Line 7: We call the func function. Then, we print out the newstring variable.

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replace-first
regular expression
clojure
communitycreator

CONTRIBUTOR

Chinweuba Elijah Azubuike

Grokking Modern System Design Interview for Engineers & Managers

Ace your System Design Interview and take your career to the next level. Learn to handle the design of applications like Netflix, Quora, Facebook, Uber, and many more in a 45-min interview. Learn the RESHADED framework for architecting web-scale applications by determining requirements, constraints, and assumptions before diving into a step-by-step design process.

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