How to capture result of replace-regexp-in-string in emacs lisp

Question

I am trying to learn Emacs Lisp. I would like to remove some white space from a string. I started with the following test case:

(defun test-fun (str)
  (interactive)
  (let ((ss str)) 
       (replace-regexp-in-string "[ ]+" "" ss)
    (message ss)))
(test-fun "He   llo")

However, evaluating this in my Scratch buffer shows that no space is removed..

abo-abo · Accepted Answer · 2013-12-02 16:32:08Z

2

Here's a correction:

(defun test-fun (str)
  (let ((ss (replace-regexp-in-string "[ ]+" "" str)))
    (message ss)))

interactive is only useful for interactive command, so you don't need it here. Also take note of order of evaluation.

answered Dec 2, 2013 at 16:32

abo-abo

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2 Comments

Håkon Hægland Over a year ago

Perfect! This works.. So the point is that replace-regexp-in-string does not change its parameter, ss, in my case, but rather returns the modified string?

Drew Over a year ago

Correct. From C-h f replace-regexp-in-string: "Return a new string containing the replacements."

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