problem with elisp

[Seweryn Kokot <sewkokot@gmail.com>]

Hello,

Could you explain to me why the following function doesn't work in the first
version and when swapping line
	(let ((string-temp (make-temp-name ""))) 
with
    (let ((string-temp "@temp@"))           
it works correctly?


(defun my-swap-string (string-a string-b)
  (interactive "sFirst string to swap: \nsSecond string to swap: ")
  (save-excursion  
	(let ((string-temp (make-temp-name ""))) ; this doesn't work
;;	(let ((string-temp "@temp@"))            ; this works
	  (goto-char (point-min))
	  (while (search-forward string-a nil t)
		(replace-match string-temp))
	  (goto-char (point-min))
	  (while (search-forward string-b nil t)
		(replace-match string-a))
	  (goto-char (point-min))
	(while (search-forward string-temp nil t)
	  (replace-match string-b)))))


Thanks in advance.
-- 
regards,
Seweryn