Is there an easy way to search for other occurences of a selected rectangle, regardless of the column at which the pattern starts?

As an example, when searching for the 4x2 text block in lines 1+2 in the sample below, it would result in two matches: one for lines 4+5, one for lines 7+8

1 qwer
2 asdf
4   qwer
5   asdf
7     qwer
8     asdf

I didn't find any easy way to do what you want, but make a my-rectangle-forward-search command myself, I am not sure what can I do when find a matching rectangle, so I just use message-box to indicate start/end poing and content of the found rectangle.

(require 'subr-x)                       ; Require Emacs 24.4+

(defun my-rectangle-equal (start1 end1 start2 end2)
  "Return t if two rectangle have identical contents."
  (when-let ((r1-lines (extract-rectangle start1 end1))
             (r2-lines (extract-rectangle start2 end2))
             (r1-line-number (length r1-lines) )
             (r2-line-number (length r2-lines) ))
    (when (and (= r1-line-number r2-line-number)
               (> r1-line-number 0))
      (setq counter 0)
      (catch 'my--break
        (while (< counter r1-line-number)
          (unless (string-equal (elt r1-lines counter)
                                (elt r2-lines counter))
            (throw 'my--break nil))
          (setq counter (1+ counter)))

(defun my-rectangle-dialog (start end)
  (interactive "r")
  (message-box (format
                "The content in [%d, %d] rectangle is: \n%s"
                start end
                (mapconcat #'identity (extract-rectangle start end) "\n"))))

(defun my-rectangle-forward-search (start end)
  "Search forward from point for the region-rectangle."
  (interactive "r")
  (when-let ((lines (extract-rectangle start end))
             (line-number (length lines))
             (first-line (car lines)))
      (let (-start -end)
        ;; (goto-char end)
        (while (re-search-forward first-line nil 'noerror)
          (setq -start (- (point) (length first-line)))
          (line-move-visual (1- line-number))
          (setq -end (point))
          ;; Do something on rectangle just find
          (my-rectangle-dialog -start -end))))))
  • Thanks. I haven't tried to look into the code yet, but when calling my-rectangle-forward-search via M-x, I get the following error: my-rectangle-forward-search: Symbol's function definition is void: when-let. – Evgeniy Berezovsky Jul 29 '15 at 22:32
  • when-let comes from subr-x.el, which requires at least Emacs 24.4. I should call (require subr-x)` before using that macro, will fix. – xuchunyang Jul 30 '15 at 3:59
  • Still no luck. Will try to see if there's something wrong with my setup (GNU Emacs 24.5.1 (x86_64-pc-linux-gnu, GTK+ Version 3.16.4) of 2015-06-29 on trouble, modified by Debian) – Evgeniy Berezovsky Jul 30 '15 at 6:24
  • @xuchunyang when-let was added in emacs 25.x. It's still in the master branch only, not yet in any stable release. – Kaushal Modi Aug 29 '15 at 19:42
  • @kaushalmodi You're right, dash.el's -when-let* can be used here for the same purpose, besides, the code also looks buggy. I think I have to update it when I have time. – xuchunyang Aug 29 '15 at 20:57

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