emacs-yank-binary-and-increment.el

;;; I needed this for Verilog. I wanted a way to put something in the Emacs kill buffer
;;; and "yank" it over and over while incrementing the first found binary value in the kill buffer.
;;; It's patterned after another solution I found elsewhere, but this is mostly my code at this point.
;;; Bog-standard dumb code I wrote because I thought I could hack it out quickly while learning Elisp. it's nothing
;;; wonderful, but maybe it will save someone some time someday.
;;;
;;; Example:
;;; Start with the text
;;;      case ({ADbool, ADsel})
;;;        5'b1010101:
;;;
;;; and select and copy to yank buffer (alt-W) the last line of the above.
;;;
;;; Then yank-binary-and-increment (C-c C-y) will paste a copy of that line each time it's invoked but
;;; with the next higher binary number in place of 5'b1010101.  Doing this twice yields:
;;;   case ({ADbool, ADsel})
;;;      5'b1010101:
;;;      5'b1010110:
;;;      5'b1010111:
;;;


(defun number-to-binary-string (number n-digits)
  (setq new-string "")
  (dotimes (digit-count n-digits)
    (setq new-string (concat (if (zerop (logand number 1)) "0" "1") new-string))
    (setq number (lsh number -1)))
  new-string)

(defun increment-first-binary-string (string)
  (setq start (string-match "'b[01]+" string))
  (setq end (match-end 0))
  (unless start (throw 'no-number))     ;Bail safely if no number found
  (setq first-string (substring string (+ start 2) end))
  (setq number (string-to-number first-string 2))
  (setq new-num-string (number-to-binary-string (1+ number) (length first-string)))
  (concat
   (substring string 0 start)
   "'b"
   new-num-string
   (substring string end)))

(defun yank-binary-and-increment ()
  "Yank text, incrementing the first integer found in it."
  (interactive "*")
  (catch 'no-number 
    (setq new-text (increment-first-binary-string (current-kill 0)))
    (insert-for-yank new-text)
    (kill-new new-text t)))

(global-set-key (kbd "C-c C-y") 'yank-binary-and-increment)