Increment and Decrement integers at the cursor

increment.el

;; check if string is an integer
(defun string-integer-p (string)
  (if (string-match "\\`[-+]?[0-9]+\\'" string)
      t
    nil))

;; Decrement Int
(defun decrement ()
  "Decrement the integer that the cursor is on."
  (interactive)
  (let ((x (thing-at-point 'symbol)))
    (when (string-integer-p x)
      (let ((x-int (string-to-number x))
            (bds (bounds-of-thing-at-point 'symbol)))
        (progn 
          (delete-region (car bds) (cdr bds))
          (insert (number-to-string (- x-int 1)))
        )
      )
    )
  )
)

;; Increment Int
(defun increment ()
  "Increment the integer that the cursor is on."
  (interactive)
  (let ((x (thing-at-point 'symbol)))
    (when (string-integer-p x)
      (let ((x-int (string-to-number x))
            (bds (bounds-of-thing-at-point 'symbol)))
        (progn 
          (delete-region (car bds) (cdr bds))
          (insert (number-to-string (+ x-int 1)))
        )
      )
    )
  )
)