Emacs isearch Whitespace Regex Setup

In emacs isearch (Alt+x isearch-forward) [see Emacs: Search Text in Current File] , you can type a space and it will also search for hyphen - and low line _ and tab and newline.

This this very convenient.

Put this in your Emacs Init File:

;; for isearch-forward, make these equivalent: space newline tab hyphen underscore
(setq search-whitespace-regexp "[-_ \t\n]+")

But sometimes you want literal. This command makes it easy to toggle.

(defun xah-toggle-search-whitespace ()
  "Set `search-whitespace-regexp' to nil or includes hyphen lowline tab newline.
Explanation: When in isearch (M-x `isearch-forward'), space key can also stand for other chars such as hyphen lowline tab newline. It depend on a regex. It's convenient. But sometimes you want literal. This command makes it easy to toggle.

Emacs Isearch Space Toggle
URL `http://xahlee.info/emacs/emacs/emacs_isearch_space.html'
Version 2019-02-22 2021-11-13"
  (interactive)
  (if (string-equal search-whitespace-regexp nil)
      (progn
        (setq search-whitespace-regexp "[-_ \t\n]+")
        (message "Space set to hyphen lowline tab newline space"))
    (progn
      (setq search-whitespace-regexp nil)
      (message "Space set to literal."))))

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