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The following counts the number of opening (brcmk-beg) and closing (brcmk-end) braces. Having brcmk-end an optional argument, I would like to print

$begmk nil $count-begmk 0

when the user either hits Return or uses a blank space when using the minibeffer with the call (read-char-from-minibuffer "Closing Bracemark: ").

    (cl-defun rk-bracemark-count-from-char
        (brcmk-beg &optional brcmk-end
                             (rgn-beg (region-beginning))
                             (rgn-end (region-end)))
      "Count number of opening and closing brace marks.
    Search is applied within a region."
    
      (interactive
       (list (read-char-from-minibuffer "Opening Bracemark: ")
             (read-char-from-minibuffer "Closing Bracemark: ")
             (region-beginning)
             (region-end) ))
    
      (save-excursion
        (let ( ($count-begmk  0) ($count-endmk  0) 
               ($begmk  (char-to-string brcmk-beg))
               ($endmk  (or (and brcmk-end (char-to-string brcmk-end))
                "nil")) )
    
          (goto-char rgn-beg)
          (while (and (< (point) rgn-end)
                      (search-forward $begmk rgn-end t))
            (cl-incf $count-begmk))
    
          (goto-char rgn-beg)
          (while (and brcmk-end
                  (< (point) rgn-end)
                  (search-forward $endmk rgn-end t))
            (cl-incf $count-endmk))
    
          (message "Marks: %s %s  Counts: %d %d" $begmk $endmk
               $count-begmk $count-endmk)
          (goto-char rgn-beg) )))

2
  • The question isn't clear. read-char-from-minibuffer cannot return "empty" or return more than one char ("composed of spaces"). Please clarify what you're asking.
    – Drew
    Apr 13, 2022 at 19:54
  • 1
    Why don't you write you own read function (based on read-char-from-minibuffer) that return nil when you don't get the input you want. I guess that would make the function use the default argument. (Personally, I haven't used cl-defun so I'm not familiar with default arguments.) Apr 13, 2022 at 20:36

1 Answer 1

1
(require 's) ; for s-blank-str-p

...
  (interactive
    (list (read-char-from-minibuffer "Opening Bracemark: ")
          (let ((x (read-char-from-minibuffer "Closing Bracemark: ")))
            (unless (s-blank-str-p (char-to-string x)) x))
          (region-beginning)
          (region-end)))
  ;; at this point brcmk-end is either nil or a closing delimiter
...
5
  • So when user hits Return, the local variable x is nil. Otherwise x gets converted to a string. Right?
    – Dilna
    Apr 13, 2022 at 21:27
  • Would I need to install the feature s?
    – Dilna
    Apr 13, 2022 at 21:29
  • I figure that the line (unless (s-blank-str-p (char-to-string x)) x) should be (unless (s-blank-str-p (char-to-string x)) x))
    – Dilna
    Apr 13, 2022 at 23:49
  • 1
    Yes, package s is in the MELPA repository (and probably others). It's a comprehensive library of string-oriented functions. Apr 14, 2022 at 11:06
  • You're quite right about the parens, fixed now. Apr 14, 2022 at 11:09

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